The sides
12-3a
12-3a
4(2a-5)=8a-40
so for perimeter we + them
(12-3a)+(12-3a)+(8a-40)
=
2a-16
First,you do,2/5+2/3,but since you will need a common denominator,you will find the least common denominator for 5 and 3.The LCD(Least Common Denominator) will be 15 since both 5 and 3 could go in 15.Now,the equation looks like this: 2/15+2/15 since whatever you do to the bottom numbers,you NEED to do to the top numbers:2 and 2.Now you will need to do,2x3,since 5x3=15 and the answer to 2x3=6 then you do 2x5,since 3x5=15 the answer is 10 now the equation looks like this:6/15+10/15 now you add them together,and the answer will be 16/15 and if you want the answer to be a mixed number,it would look like this: 1 1/15. Hope this helps!
The answer is 11 if i recall correctly.