Answer:
<em>x+y=4</em>
Step-by-step explanation:
hello :
note : by identity you have x²-y² = (x-y)(x+y)
in this exercice : 2x²-2y² = 2(x²-y²) = 2 (x-y)(x+y)
means : 2 (x-y)(x+y) = 40
but x-y = 5
so : 2(5)(x+y) =40
x+y=40/10
<em>x+y=4</em>
The angles inside a triangle always add up to 180 degrees.
The whole thing is one big triangle made of two smaller ones.
28 + 58 + 77 + x = 180
163 + x = 180
x = 180 - 163
x = 17