1st add 7 to both sides : 3z = 21, 2nd divide both sides with 3: z = 7
90x = 12
Divide both sides by 90
x = 0.1333....
Move the decimal to places to the right.
13.333% repeating.
x
=
−
7
or
x
=
−
8
Explanation:
Find a pair of factors of
56
with sum
15
.
The pair
7
,
8
works in that
7
⋅
8
=
56
and
7
+
8
=
15
Hence:
0
=
x
2
+
15
x
+
56
=
(
x
+
7
)
(
x
+
8
)
So:
x
=
−
7
or
x
=
−
8
Alternative method
The amount of sales taxes rounded to the nearest hundredth is 0.97