<PRE><B>Question 99562</B>
The perimeter of a rectangle can be expressed as 
2 times its length plus 2 times its width
So perimeter of the given rectangle would be
{{{2(3x-4)+2(7x+10)}}}
to simplify first remove the parentheses by multiplying the 2 across 3x-4
and the multiplying the other 2 across 7x+10
{{{6x-8+14x+20}}}
next combine like terms 6x + 14x and -8+20
{{{20x+12}}}
thats it.</PRE>