1. The problem is to simplify the expression $20rx4$. 2. This expression represents multiplication of the numbers and variable: $20 \times r \times 4$. 3. According to multiplication rules, multiplication is associative and commutative, so we can rearrange and group the numbers: $$20 \times 4 \times r$$ 4. Multiply the constants first: $$20 \times 4 = 80$$ 5. So the expression simplifies to: $$80r$$ 6. Therefore, the simplified form of $20rx4$ is $80r$.