2x-3y=4
x+4y=-9/*(-2)
2x-3y=4
-2x-8y=18
-11y=22/:(-11)
y=-2
x+4*(-2)=-9
x-8=-9
x=-1
I hope this helped.
Answer:
using identity (a+b)(a-b) = a^2 -b^2
Multiply 12x15 and multiply 8x5
Then subtract their answers to find the remaining that's colored red.