Solve the system by substitution.
y = -2x
y = -9x+21

Nine more than four times a number is the same as one less than twice the number. find the number?

Tabby sells clothing at a retail store, and she earns a commission of 6.25% on all items she sells. last week she sold a pair of jeans for $32.50, a skirt for $18.95, and 2 blouses for $14.95 each. what was tabby's total commission? a $4.15 b $5.08 c $81.35 d $348.60

For f(x) = 3x+1 and g(x) = x2 - 6, find (g/f)(x)