Answer:
x=4 and y=4
Step-by-step explanation:
From first function we have:

And from the second one:

Substitute them:

You can use 10 blocks by having 1 ten and 6 ones and then divide it into groups of 3 when you do that you are kind of subtracting when you take away 3 away each time. After that you multiply it, so you think of whatever times 3 is 16 which is 15 r1. Then your answer should be 30.
30 x 30 = 900
This is the surface area of one side
900 x 6
Multiply by 6 to get the surface area of all 6 sides of the cube
900 x 6 = 5400