I need help please i don’t understand how to solve

Do 3x+15+10x+9=180 and solve that. Once you have done that take your answer and substitute the x in 3x+15 and solve that. Since 3x+15 and the basement angle is vertical whatever your answer is, is the angle of the basement

Step-by-step explanation:

This could not be exactly right but it is what I think it is

we have three similar triangles, because each has a right angle and shares an angle.   let's write the angles in order: opposite to short leg, long leg, hypotenuse.

cab similar to bad similar to cbd

or as ratios,

ca: ab: cb = ba: ad: bd = cb: bd: cd

we also know

ac = ad + cd

(ad+cd): ab: cb = ba: ad: bd = cb: bd: cd

(ad+cd)/cb=cb/cd

we have cb=6, ad=5 and seek x=cd.

we reject the negative root and conclude x=4

answer: 4