The longest side is 5/(5+3+4) = 5/12 of the perimeter, hence
(5/12)*156 cm = 65 cm . . . . . the length of the longest side
They stayed at the beach for 7 days. 4 x 3 = 12. 12 - 5 = 7
Answer:
A. 
Step-by-step explanation:
The options are:

For this exercise it is important to remember that, by definition, the Exponential parent functions have the form shown below:

Where "a" is the base.
There are several transformations for a function f(x), some of those transformations are shown below:
1. If
and
, then the function is stretched vertically by a factor of "b".
2. If
and
, then the function is compressed vertically by a factor of "b"
Therefore, based on the information given above, you can identify that the function that represents a vertical stretch of an Exponential function, is the one given in the Option A. This is:

Where the factor is:

And 
Gave away 7 ⇒ -7
Bought 6 ⇒ + 6
Left with 13
If he did not buy the 6 cars ...
13 - 6 = 7
If he did not give the 7 cars away ...
7 + 7 = 14
He has 14 cars at first.
13 - 6