If youre writing an exprssion all you need to do is make variables and multiply by the given number A, C, and S will be our variables.
2A + 3C + 1S = Total cost for andrews family
4A + 2C = Total cost for Spencers family
Now, Does 2A + 3C + 1S = 4A + 2C
lets say A = 5 , C = 3 , and S = 2
2(5) + 3(3) + 1(2) = 4(5) + 2(3)
10 + 9 + 2 = 20 + 6
21 = 26
if this is your example then No, the spencers family spent more than the andrews family, youll have to do the math differently and may come up with a different answer if you were given values that you didn't give us, but this is how its done :)
Hope this helps!
<span>A = P(1+r/2)^2t
A/P = (1+r/2)^2t
ln(A/P) = 2t ln((1+r/2))
ln(A/P)/ln(1+r/2) =2t
ln(9000/4190.51)/ln(1+0.052/2)=2t
t=15 yrs
therfore ans is C.14 years ,11 months</span>