Solve the System by substitution

y=9x
y=3x+12

A25-inch wide drum is used in a marching band. what area does the top of the drum cover? round to the nearest hundredth. (use 3.14 for pi.)

1. writing an equation for an exponential function by 2. a piece of paper that is 0.6 millimeter thick is folded. write an equation for the thickness t of the paper in millimeters as a function of the number n of folds. the equation is t(n)= 3. enter an equation for the function that includes the points. (-2, 2/5) and (-1,2)

Afamily went out to dinner and their bill was $113.if they want to leave a 19% tip, how much should they leave.