To substitute the value $7$ for the variable $b$ in the expression $5b - 2$, follow these steps to replace $b$ with $7$ and simplify the expression.

When substituting a value into an algebraic expression, you replace the variable with the specified number. In this case, we have the expression $5b - 2$, and we will substitute $7$ for $b$. Begin by rewriting the expression with $7$ in place of $b$:

Next, carry out the multiplication. Multiply $5$ by $7$ to obtain $35$. Therefore, the expression simplifies to:

Finally, subtract $2$ from $35$. This calculation yields $33$. Thus, when you substitute $7$ for $b$ in the expression $5b - 2$, the simplified result is $33$.

This substitution process is fundamental in various branches of mathematics, including solving equations and evaluating functions. By mastering the technique of substituting values, you can more effectively manipulate algebraic expressions and solve problems with greater efficiency.