Answer
$t=-2$
Work Step by Step
The given equation is
$\Rightarrow 5-t=7t+21$
Add $t-21$ to each side.
$\Rightarrow 5-t+t-21=7t+21+t-21$
Add like terms.
$\Rightarrow -16=8t$
Divide each side by $8$.
$\Rightarrow \frac{-16}{8}=\frac{8t}{8}$
Simplify.
$\Rightarrow -2=t$
Check $t=-2$.
$\Rightarrow 5-(-2)=7(-2)+21$
$\Rightarrow 5+2=-14+21$
$\Rightarrow 7=7$
True.
