1. **State the problem:** Simplify the expression $ (3x + 2x)(5x + 1x) $. 2. **Combine like terms inside each parenthesis:** $$ 3x + 2x = 5x $$ $$ 5x + 1x = 6x $$ 3. **Rewrite the expression:** $$ (5x)(6x) $$ 4. **Multiply the coefficients and variables:** $$ 5 \times 6 = 30 $$ $$ x \times x = x^2 $$ 5. **Final simplified expression:** $$ 30x^2 $$ This means the product of the two binomials is $30x^2$.