<span>By multiplying the first function with number 5, the graph will stretch by the order of five, meaning that in the second graph every value of the x will correspond to the 5 times bigger value of y than in the first case. Due to the +6 component, the second graph shifts to the left by 6 units.</span>
I think this is more of an opinion question. What someone could solve mentally may not be the same as someone else's.If it were my worksheet, I'd circle all of them but it may be different for you.
At your level, I'd probably circle:
54 - 10
93 - 20
and 39 - 2
To get the area, you do 13 * 9, which is 117, and the perimeter is 13+13+9+9 which is 44 :)