Answer
$y=5$
Work Step by Step
$4(y+1)-3=21$ $\longrightarrow$ apply distributive property
$4y+4-3=21$ $\longrightarrow$ simplify
$4y+1=21$ $\longrightarrow$ subtract 1 from each side
$4y+1-1=21-1$ $\longrightarrow$ simplify
$4y=20$ $\longrightarrow$ divide each side by 4
$4y\div4=20\div4$ $\longrightarrow$ simplify
$y=5$
