The answer is D: -1
If you plug it in, it’s the only one that works
0.4 * x = 68
x = 68/0.4
x = 170
check:
0.4 * 170 = 68
Area of a rectangle = length (l) * width (w)
A = 30ft * 20ft
A = 600 sq ft
Now the width of a sidewalk that surroundeds it = 3 ft
so now the area of the rectangle with sidewalk= 30+3ft * 20+3ft
A = (33*23) ft
A = 759 sg ft
Area of the sidewalk = 759 - 600
A = 159 sq ft
To double the principle the formula is
2p=p e^rt
2=e^rt
2=e^0.12t
Solve for t
T=(log(2)÷log(e))÷0.12
T=5.78 years
