Corresponding sides of similar shapes or figures are proportional to each other. Since ∆LMN ~ ∆OPQ, the ratio of their corresponding sides would therefore be equal. Thus:
(-6) multiplies both terms inside parentheses. For some reason, the student changed the sign of that multiplier for the second term. The second term of the result should have a positive sign, the result of multiplying (-6)(-2/13) = +12/13.