Question

i know you doy+18 + y+48 + y+18 = 180 but i always get things wrong.

Answer 1

The external angle of the triangle is equals to the sum of the 2 opposite angles. Therefore,

$\begin{gathered} y+48=y+18+y+18 \\ y+48=2y+36 \\ \text{combine like terms} \\ 48-36=2y-y \\ y=12 \end{gathered}$