Answer
$${65^ \circ }{\text{ and 11}}{{\text{5}}^ \circ }$$
Work Step by Step
$$\eqalign{
& {\left( {3x + 5} \right)^ \circ } + {\left( {5x + 15} \right)^ \circ } = {180^ \circ } \cr
& 3x + 5 + 5x + 15 = 180 \cr
& 8x + 20 = 180 \cr
& 8x = 160 \cr
& x = \frac{{160}}{8} \cr
& x = 20 \cr
& \cr
& {\left( {3x + 5} \right)^ \circ } = {\left( {3\left( {20} \right) + 5} \right)^ \circ } = {65^ \circ } \cr
& {\left( {5x + 15} \right)^ \circ } = {\left( {5\left( {20} \right) + 15} \right)^ \circ } = {115^ \circ } \cr
& \cr
& {65^ \circ }{\text{ and 11}}{{\text{5}}^ \circ } \cr} $$
