Find the y-intercept of the line on the graph

Compare these two waves: the blue and orange waves have the same pitch, but the blue wave is louder. the blue and orange waves have the same volume, but the blue wave has a higher pitch. the orange wave has a higher pitch, but the blue wave is louder. the blue wave has a higher pitch, but the orange wave is louder.

The angle of a triangle are given as 6x,(x-3), and (3x+7). find x then find the measures of the angles

How do i do this? i don’t understand