Help please...........

so the probably seems impossible b/c there is some "implied" knowledge. You are supposed to remember that interior angles of a triangle add up to 180 °. Which I bet you knew.. .huh

so let's put that knowledge to work to help us solve this

we can say that all of the angles add up to 180 like this:

180 = (x-4) + (11x-11) + (x+13)

see? now group all the like terms, that is, put the x'es together & the numbers

180 = 13x -2

see? I just grouped the x terms and the constant terms, now move the 2 arcoss the equal sign to the other side, by adding 2 to both sides

182 = 13x

see? now divide both sides by 3 :)

14 = x

now we know what x is so plug that into the expression for the C angle

∠C = x-4

∠C = 14-4

∠C = 10 °

there you go. :)

best of luck, just leave a message in the comments if you have more questions , I'll see it there :)