Theresa sells lemonade for $1, juice for $1.50, and coffee for $2. on one day, the number of coffees she sells is twice the number of lemonades she sells, and 4 more than the number of juices she sells. if she earns a total of $74, how many lemonades did she sell?

answer: -10

step-by-step explanation:

s(t) = 1 - 10t

s(x) = 1 - 10x

s(x + h) = 1 - 10(x + h)

            = 1 - 10x - 10h

s(x + h) - s(x) = 1 - 10x - 10h - (1 - 10x)

                      = 1 - 10x - 10h - 1 + 10x

                      = -10h

= -10