Carmen earned 3 * $4 = $<<3*4=12>>12 at the green house.
She earned 2 * $3.50 = $<<2*3.5=7>>7 for the mints.
She earned $7 + $5 = $<<7+5=12>>12 at the yellow house.
She earned 9 * $2 = $<<9*2=18>>18 at the brown house.
So, Carmen earned a total of $12 + $12 + 18 = $<<12+12+18=42>>42.
#### 42