need help algebra 2 its urgent

Question

Find the area of a triangle bounded by the y-axis, the line f(x)=10-2x, and the line perpendicular to that passes through the origin. 

Answer 1

the perpendicular line through the origin is y=x/2 It has slope = the negative inverse of -2

the perpendicular lines intersect at (4,2) set 10-2x=x/2 and solve for x=4, y=4/2 =2

The triangle with vertices (4,2), (0,0) and (0,10) form a right triangle with Area =bh/2 = 10(4)/2 = 20