The 2 smaller triangles are similar. Thus, y is to z as x is to 4. You need 3 such ratios to find the 3 unknowns. Could you try your hand at writing 1 more ratio based upon the illustration?
A line adds up to equal 180 degrees. And adjacent angles also add to equal 180 since they share a side on a line. So add them together and make them equal 180 9x - 7 + 8.5x + 4 = 180 17.5x - 3 = 180 17.5x = 183 x = 10.5
