450s+150c=5700 and
450s+300c=7800 so subtracting the 2nd from the first gives you:
-150c=-2100
c=$14.00 and since 450s+300c=7800
450s+14(300)=7800
450s=3600
s=$8.00
So senior tickets are $8.00 and children's tickets are $14.00
....
A=40+10L, B=30+12L
A=B when
40+10L=30+12L
-2L=-10
L=5
So A and B will cost the same when purchasing five lines.
The cost for 5 lines is:
30+12L=30+60=90
So five lines cost $90 under either plan.
If you needed four lines:
A=40+40=80, B=30+48=78
So if you only need four lines B is cheaper at $78, $2 less than A.
....
11(3S+14L=203) and -3(11S+11L=220) gives you:
33S+154L=2233 and -33S-33L=-660 adding these two together yields:
121L=1573
L=$13.00 which makes 3S+14L=203 become
3S+14(13)=203
3S+182=203
3S=21
S=$7.00
So a small box costs $7.00 and a large box costs $13.00
