Final answer:
Juan tutored 7.5 hours in chemistry last week when he tutored 12 hours total. The equation x + 3x + (2x - 3) = 12 can be used to determine this.
Step-by-step explanation:
To determine how many hours Juan tutored in chemistry last week, we can set up an equation based on the given information. Let's assume that Juan tutored x hours in math. According to the problem, he tutored 3 times as many hours of chemistry as math, so he tutored 3x hours in chemistry. He also tutored 3 less than twice as many hours of Spanish as math, so he tutored 2x - 3 hours in Spanish. The total tutoring hours last week was 12, so the equation is:
x + 3x + (2x - 3) = 12
Simplifying the equation, we have:
6x - 3 = 12
Adding 3 to both sides of the equation, we get:
6x = 15
Dividing both sides of the equation by 6, we find that:
x = 2.5
Therefore, Juan tutored 2.5 hours in math last week. To find the number of hours in chemistry, we can substitute x = 2.5 into the expression 3x to get:
3(2.5) = 7.5
Therefore, Juan tutored 7.5 hours in chemistry last week.