How does tripling the side lengths of a pentagon affect its perimeter

The perimeter is three times the old.

Because if the formula is
P= a+b+c and you triple each side you get P= 3a+3b+3c so it would be three times as big as the old perimeter.

For example if your equation is
P=3+2+5 (which equals 10) and then you multiply each side by 3 your new formula is P= (3•3) (3•2) (3•5) which equals 30. 30 is three times larger than 10.

Hope this helps!