Solve each system by elimination 9x - 6y = -21 and -9x + 9y = 18

1. are the triangles similar and if so why? what is the value of x? show your work.

Determine which expressions represent real numbers and which expressions represent complex number. asaaap! plis!

What is the next step in the given proof? choose the most logical approach. a. statement: m 1 + m 2 + 2(m 3) = 180° reason: angle addition b. statement: m 1 + m 3 = m 2 + m 3 reason: transitive property of equality c. statement: m 1 = m 2 reason: subtraction property of equality d. statement: m 1 + m 2 = m 2 + m 3 reason: substitution property of equality e. statement: 2(m 1) = m 2 + m 3 reason: substitution property of equality