Hours He will work in this Week=20 hours.
Number of Hours he will Teach=x
Number of Hours He will Eat icecream=y
We know
x+y=20
x=20-y (Equation 1)
Teaching French=$12
Eating Icecream=$8
Let He Total Money he Earn from Teaching.
=12×Number of Hours he work
=$12x
Eating Icecream=$8
Total money spent=$8y
But Total Money=$190
MEANS
$12x+$8y=$190
12(20-y)+8y=190
240-12y+8y=190
-4y=190-240
-4y=-50
y=50/4
y=12.5
We know x+y=20
x+12.5=20
x=20-12.5
x=7.5 hours
MEANS He have to teach At least =7.5 hours.To make $190