ShmoopTube

Where Monty Python meets your 10th grade teacher.

Search Thousands of Shmoop Videos

ACT Math 2.5 Elementary Algebra 279 Views

Share It!

Description:

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

Language:

English Language

Subjects:

Tags:

Common Core Standards:

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.
Full Transcript