If there was something like <em><u>5z</u></em> + 5x <em><u>-</u></em><em><u> </u></em><em><u>3z</u></em> + 5y, then both 5z and -3z have something in common and so therefore are said to be like terms.
If I understand the drawing correctly than yes, because 6 9/12 + 6 9/12 = 12 and 18/12 = 13 and 6/12 or 13 and 1/2. 13 1/2 + 4 8/12 = 13 6/12 + 4 8/12 = 17 and 14/12 = 18 2/12 or 18 and 1/6.
