What’s the equation of this red line?

Suppose your school costs for this term were $4900 and financial aid covered 3/4 of that amount. how much did financial aid cover? and how much do you still have to pay?

What is the missing reason in the proof? segment addition congruent segments theorem transitive property of equality subtraction property of equality?

Write the percent as a fraction or mixed number in simplest form. 0.8%