Question

r - 20 = 19A. Add 20 to both sides B. Subtract 20 from both sides C. Add 19 to both sides D. Subtract 19 from both sides

Answer 1

$\begin{gathered} r-20=19 \\ \text{add 20 to both sides} \\ r-20+20=19+20 \\ r=39 \end{gathered}$

The answer is A. we add 20 to both sides to isolate the variable r.