Answer: X=12
Explanation: 180-72= 108. 108 divided by 9 is 12
Treat the matrices on the right side of each equation like you would a constant.
Let 2<em>X</em> + <em>Y</em> = <em>A</em> and 3<em>X</em> - 4<em>Y</em> = <em>B</em>.
Then you can eliminate <em>Y</em> by taking the sum
4<em>A</em> + <em>B</em> = 4 (2<em>X</em> + <em>Y</em>) + (3<em>X</em> - 4<em>Y</em>) = 11<em>X</em>
==> <em>X</em> = (4<em>A</em> + <em>B</em>)/11
Similarly, you can eliminate <em>X</em> by using
-3<em>A</em> + 2<em>B</em> = -3 (2<em>X</em> + <em>Y</em>) + 2 (3<em>X</em> - 4<em>Y</em>) = -11<em>Y</em>
==> <em>Y</em> = (3<em>A</em> - 2<em>B</em>)/11
It follows that

Similarly, you would find

You can solve the second system in the same fashion. You would end up with

Answer:
1560
Step-by-step explanation:
First (2 1/2)/(1/4) = (5/2)(4) = 20/2 = 10
Next, 3/(1/4) = 3(4) = 12
Lastly, (3 1/4)/(1/4) = (13/4) x 4 = 52/4 = 13
This means we need 10 rows of 12, 13 high. 10(12)(13) = 1560 cubes.
Another way is to multiply 2 1/2 x 3 x 3 1/4 = 5/2 x 3 x 13/4 = 195/8
A 1/4 inch cube is 1/4 x 1/4 x 1/4 for a volume of 1/64
(195/8)/(1/64) = (195/8)(64) = 1560 cubes.