8 and 20 are not factors of 150. The divisibility rules can be used to show that 1, 2, 3, 5, 6, and 10 are factors (and that 4 and 9 are not). Use factor pairs to find more factors: 15, 25, 30, 50, 75, and 150. Use division to check 7, 8, 11, 12, and 13. Since $\displaystyle{150}\div{13}\usepackage{cmbright}\Huge\$ is less than 13, stop. The correct answer is 1, 2, 3, 5, 6, 10, 15, 25, 30, 50, 75, and 150.