Equations, inequalities and simultaneous models.

Answer: −6

1. Add the equations: 6x=−36.
2. Therefore x=−6.

Answer: 19

1. Add the equations to find x=16;
2. subtract them to find y=3.
3. Hence x+y=19.

Answer: 255

1. Solve the two price equations: adult $36, student $20.
2. Discounted adults cost $27 each.
3. Total =5×27+6×20= $255.