Which question? Perimeter means to add each side together to find a total. The sides with the same markings are equal ... In number 9. All three sides are equal and the entire shape is 45, so 3(unknown)=45
3(x) = 45 then to get the 3 off the x you divide both sides by 2
3x/3 = 45/3
1x = 15
Thus the answer is each side is 15...