The commission is calculated by multiplying the percentage by the value sold, in this case we have two commission rates, one for the first 1000 F and one for the remaining 6500 R, so to calculate the total commission C each commission must be calculated and add them:
[tex]F = 0.12 * \$1000 = \$120\\R = 0.15 * \$6500 = \$975\\C = F + R = \$1095[/tex]
Answer
Oscar's commission last month was $1095