It was complicated but I did it
We go from 10x+20 = 50 to 10x = 30 after we subtract 20 from both sides. So we use the subtraction property (of equality).
Answer: Choice D
A - area of a trapezoid;
a, b - two bases.
A = h * ( a + b ) / 2 / * 2 ( we have to multiply both sides by 2 )
2 A = h *( a + b )
2 A = h a + h b
h b = 2 A - h a
b = ( 2 A - h a ) / h
b = 2 A/h - a
Answer: D )
B: 3 and 4 because they both do not have an = sign
