First, we need to find out x value. So:
We know that the sum of the 3 angles equals 180º. Then:
[tex]\begin{gathered} (3x\text{ -1\rparen + \lparen10x-8\rparen + \lparen4x+2\rparen= 180^^ba} \\ 3x\text{ -1 + 10x - 8 + 4x +2 = 180} \\ 17x\text{ -7 = 180} \\ 17x=\text{ 180 + 7} \\ 17x\text{ = 187} \\ x=\text{ }\frac{187}{17} \\ \\ x=\text{ 11} \\ \\ Then,\text{ if x= 11: } \\ m\angle PHE=\text{ }10x\text{ -8} \\ m\angle PHE=\text{ 10\lparen11\rparen- 8} \\ m\angle PHE=\text{ 110 -8} \\ m\angle PHE=\text{ 102^^ba} \end{gathered}[/tex]
