The expression is .
According to subtraction property of equality: if , then
.
(Subtract 7 from each side)
(Additive inverse property:
)
(Subtract:
)
According to subtraction property of equality: if , then
.
(Subtract 5x from each side)
(Commutative property: a + b = b + a)
(Additive inverse property:
)
(Subtract:
)
According to division property of equality: if , then
.
(Divide each side by 3)
(Cancel common terms)
(Divide:
)
The value of .