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ACT Math Videos 164 videos

ACT Math 1.1 Pre-Algebra
1061 Views

Pre-Algebra Drill 1, Problem 1. Calculate 23 + 53(7 – 4).

ACT Math 1.1 Trigonometry
355 Views

ACT Math: Trigonometry Drill 1, Problem 1. What is the length of y?

ACT Math 1.2 Coordinate Geometry
252 Views

ACT Math: Coordinate Geometry Drill 1, Problem 2. Solve the inequality and determine which solution is shown on the number line.

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ACT Math 2.5 Elementary Algebra 280 Views


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Description:

ACT Math Section: Elementary Algebra Drill 2, Problem 5. Use these two equations to solve for both x and y.

Language:
English Language

Transcript

00:02

Here's your shmoop du jour:

00:05

Solve for x and y: 3x + 2y = 13 6x + y = 20

00:11

And here are the potential answers...

00:20

OK. Not much of a brain-squeezer.

00:23

Since y, stands alone in the bottom equation, let's solve for y.

00:27

We get y equals 20 minus 6x.

00:30

Now we just substitute 20 minus 6x anywhere we see a y.

00:34

Ok so rewrite the above equation with that substitution and we have

00:37

3x plus 40 minus 12x equals 13

00:41

Simplify to get negative 9x equals 13 minus 40 or negative 9x equals negative 27; divide

00:48

both sides by negative 9 and we get x equals 3.

00:52

Phew. Great. Only A and B are possible answers.

00:55

Now just plug in 3 for x in the second equation

00:58

and we get 6 times 3 is 18... plus y... equals 20.

01:02

Now subtract 18 from both sides and we get y equals 2.

01:06

Here we go. So boom! The answer is B.

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