David M. answered 01/21/19
Dave "The Math Whiz"
We have 2 unknowns, so we must have 2 equations to solve this.
Let x=pre-tax amt in city 1
y=pre-tax amt in city 2
Eq. I: y = x - 1500
Eq. II Amount of total tax = $420
9.5%x + 9.0%y = 420
.095x + .090y = 420
Using the value for y from Eq. I in Eq. II we can solve for x:
.095x + .090y = 420 Eq. II
.095x + .090(x-1500) = 420 substitute for y
.095x + .090x - 135 = 420 distributive property
.185x = 420 + 135 combine like-terms
.185x = 555 simplify
x = 555/.185 divide both sides by .185 to isolate x
x = 3000
Using Eq. I we can solve for y:
y = x - 1500 Eq. I
y = 3000 - 1500 substitute for x
y = 1500
Therefore, the pre-tax amount from city 1 was $3000 and from city 2 was $1500.