### Instruction: Expand $(x+10)(2y+10)$.### Response: To expand a product of two binomials, I can use the distributive property twice: $(x+10)(2y+10) = (x+10)(2y) + (x+10)(10)$.
Then, I can distribute again inside each pair of parentheses: $(x+10)(2y) = x(2y) + 10(2y)$ and $(x+10)(10) = x(10) + 10(10)$.
Simplifying, I get $x(2y) + 10(2y) + x(10) + 10(10) = 2xy + 20y + 10x + 100$.