How do you justify each step of this 2(8u+2)=3(2u-7)

Given right triangle xyz, which correctly describes the locations of the sides in relation to

The radius of the earth is two times the radius of the moon. what fraction of the volume of the earth is the volume of the moon?

1. ∠1 is complementary to ∠2 and ∠3 is complementary to ∠2. subtraction property of equality 2. m∠1 + m∠2 = 90 and m∠3 + m∠2 = 90 substitution 3. m∠1 + m∠2 = m∠3 + m∠2 definition of complementary 4. m∠1 = m∠3 given