230 algebra De mystif ieD
- The original amount is increased by 25%. Let x represent the original
amount.
xx
xx
x
x
x
+=
+=
+=
=
=
02516
1025 16
1025 16
12516
16
1
.
.
(.)
.
. 225
x= 12. 8
The original box of cereal contained 12.8 ounces.
- The total bill is the cost of the meal plus the tax on the meal plus
the tip.
Let x represent the cost of the meal, so the amount of the tax is 0.075x.
The tip is 15% of the meal plus tax: (x + 0.075x = 1.075x is the price of
the meal including tax), so, the tip is 0.15(1.075x) = 0.16125x.
The total bill is x + 0.075x + 0.16125x. We want this to equal 45:
meal taxtip total
xx x
xx
++ =
+
0 075 0 16125 45
10075
..
. ++=
++ =
=
0 16125 45
10075 0 16125 45
1 23625 45
.
(. .)
.
x
x
x
x^445
1 23625
36 40
.
x≈.
The couple can spend $36.40 on their meal.