We have changed our privacy policy. In addition, we use cookies on our website for various purposes. By continuing on our website, you consent to our use of cookies. You can learn about our practices by reading our privacy policy.

ShmoopTube

Where Monty Python meets your 10th grade teacher.

Search Thousands of Shmoop Videos


Linear equations Videos 7 videos

ACT Math 1.3 Elementary Algebra
301 Views

ACT Math Elementary Algebra: Drill 1, Problem 3. Solve for y using substitution.

ACT Math 1.4 Elementary Algebra
337 Views

Math Elementary Algebra: Drill 1, Problem 4. Solve for y using substitution.

ACT Math 1.5 Elementary Algebra
264 Views

Math Elementary Algebra: Drill 1, Problem 5. Solve for a using substitution.

See All

ACT Math 1.4 Elementary Algebra 337 Views


Share It!


Description:

Math Elementary Algebra: Drill 1, Problem 4. Solve for y using substitution.

Language:
English Language

Transcript

00:03

Shmoopy-Doo, where are you?

00:07

Solve for y using substitution: 3x + 4y = 15 -2x + 6y = 12

00:15

And here are the potential answers...

00:23

OK so what is this question asking?

00:24

It's just another isolation and plugging problem.

00:27

We have to solve for y by getting rid of x.

00:30

to draw any undue attention.

00:30

Then we just solve for y as in any normal, one variable problem.

00:34

So let's take the first equation and rewrite to get 3x equals 15 minus 4y.

00:41

Now divide both sides by 3 and we have x equals 5 minus 4/3 y

00:48

Then we just substitute 5 minus four-thirds y inside of x in the next equation

00:57

and we get negative 2 times the quantity 5 minus four-thirds y...plus 6y equals 12.

01:07

We distribute the negative 2 to get negative 10 PLUS eight-thirds y plus 6y equals 12.

01:16

Simplify a bit more by rewriting as negative 10 plus 8y over 3 plus 18y over 3... because

01:23

6 can also be written as 18 over 3, which gives us common denominators... equals 12.

01:31

Dealing with just the fractions we get 18 plus 8 which is 26y... over 3.

01:36

Add 10 to both sides of the equation and we can simplify everything to 26 y over 3 equals 22.

01:43

Multiply both sides by 3 over 26, and we get y equals 66 over 26.

01:56

The greatest common factor of 66 and 26 is 2 so we can simplify this to 33 over 13.

02:03

So our correct answer for y is B.

02:05

As in, 'Burlap sack.'

Related Videos

ACT Math 3.1 Plane Geometry
2559 Views

ACT Math: Plane Geometry Drill 3, Problem 1. What is the area of the trapezoid shape in the video?

Inequalities in Number Lines
3235 Views

ACT Math: Coordinate Geometry Drill 1, Problem 1. Which inequality is expressed by the number line?

ACT Math 3.1 Intermediate Algebra
1956 Views

ACT Math: Intermediate Algebra: Drill 3, Problem 1. Find the fifth number in the series.

CAHSEE Math 6.2 Algebra I
290 Views

CAHSEE Math: Algebra I Drill 6, Problem 2. Simplify the polynomial.