You can because you already know the number is 3 and the blank number is n
Let's call the width: w
the lenght is then 3w+4 ("4 more than 3 times the width")
and the parameter would be 2(w+3w+4), that is 2*(4w+4), that is 8w+8.
this is also equal to 18.4:
8w+8=18.4
8w=10.4
w=1.3
this is the width, and the lenght is:
4+3*1,3=4+3.9=7.9
and the area is their product:
1.3*7.9=10.27
R=4% or .04
a=75
y=a(1+r)^w
y=75(1+.04)^w
y=75 (1.04)^w
It would be 12
12^2 + 9^2 is 225
15^2 is 225
therefore 12^2+9^2=15^2