10a) x = 81 y = 30.5
Isolate y
2y + 20 = x
2y = x- 20
y = x/2 - 10
Plug in for y
4y - 6 + 64 + x = 180
4(x/2 - 10) - 6 + 64 + x = 180
4x/2 - 40 -6 + 64 + x = 180
4x/2 + 18 = 180
4x/2 = 162
4x = 324
x = 81
Plug in for x
2y + 20 = x
2y + 20 = 81
2y = 61
y = 30.5
10b) x = 47
Isolate x
4x -12 = 3x + 35
x - 12 = 35
x = 47
11)
2. definition of parallelogram
3. < ABD ≅ < BDC
4. < CBD ≅ <BDA
6. I'm not 100% sure what this one is but I think it has something to do with the line of symmetry.
Hope this helps! ;)