Question 307528
Assuming that x and y are the lengths of the sides of the parallelogram, then the perimeter is given by:
{{{P = 2x+2y}}} Substituting {{{P = 42}}} we have...
{{{42 = 2x+2y}}} Factoring a 2 from the right side then dividing both sides by 2, we get...
{{{21 = x+y}}} or {{{x+y = 21}}}
Now if y = 8, then...
{{{x+8 = 21}}} Subtracting 8 from both sides, we get...
{{{x = 13}}}