well, on the grid, the base RT of a triangle goes from -5 to 5, namely is 10 units long.
the height of each triangle is 5 as well, notice from 0 to 5.
[tex]\bf \stackrel{\textit{area of one triangle}}{\cfrac{1}{2}(10)(5)}\implies 25~\hspace{13em}\stackrel{\textit{both triangles added up}}{25+25\implies 50}[/tex]
