4. Km wants to order pizza for her sister's birthday. She compares two pizza places to determine which
has the best deal for her. Papa Joanna's charges a rate
of $17 for each pizza with free delivery. Domenico's
charges a rate of $13.50 each pizza plus a delivery fee
of $21. The system of equations shown models the
total costs for buying x pizzas at each.
Papa Joanna's: y = 17x
Domenico's: y = 21 + 13.5x
How many pizzas would Kim need to order for the
total cost to be the same at both pizza places?

Aspacecraft can attain a stable orbit 300 kilometers above earth if it reaches a velocity of 7.7 kilometers per second. the formula for a rocket's maximum velocity v in kilometers per second is vequalsminus0.0098tplusc ln upper r, where t is the firing time in seconds, c is the velocity of the exhaust in kilometers per second, and r is the ratio of the mass of the rocket filled with fuel to the mass of the rocket without fuel. find the velocity of a spacecraft whose booster rocket has a mass ratio of 20, an exhaust velocity of 2.1 km/s, and a firing time of 15 s. can the spacecraft achieve a stable orbit 300 km above earth?