Calculate: -7d+3+8=15

Expression: $-7d+3+8=15$

Add the numbers

$-7d+11=15$

Move the constant to the right-hand side and change its sign

$-7d=15-11$

Subtract the numbers

$-7d=4$

Divide both sides of the equation by $-7$

$\begin{align*}&d=-\frac{ 4 }{ 7 } \\&d=-0.\overset{ \cdot }{ 5 } 7142\overset{ \cdot }{ 8 } \end{align*}$