[tex]\text{If}\ \triangle ABC\cong\triangle DE F, \text{then}\\\\m\angle A=m\angle D,\ m\angle B=m\angle E\ \text{and}\ m\angle C=m\angle F\\\\\text{Therefore we have the equation:}\\\\8x-1=87\qquad\text{add 1 to both sides}\\\\8x=88\qquad\text{divide both sides by 8}\\\\\boxed{x=11}\\\\\text{We know, the sum of measures of the angles in a triangle is 180}^o.\\\\\text{Therefore:}\\\\m\angle F=180^o-(42^o+87^o)\\\\m\angle F=180^o-129^o\\\\m\angle F=51^o\\\\\text{We have the equation:}[/tex]
[tex]3y=51\qquad\text{divide both sides by 3}\\\\\boxed{y=17}\\\\Answer:\ \boxed{x=11\ and\ y=17}[/tex]
