The equation is
.
Distribute terms using distributive property:
.

(Multiply:
)
Apply commutative property of addition: a + b = b + a.
\
(Subtract:
)
Apply subtraction property of equality: If a = b then a
c = b
c.
(Subtract 15 from each side)
(Apply additive inverse property:
)
(Subtract:
)
Apply division property of equality: If a = b then
.
(Divide each side by 2)
(Cancel common terms)
(Divide:
)
The value of
.