I need help solving literal equations

Abus ride for a senior citizen cost $1.25. a monthly pass costs $35. write and inequality that represents the number of times a senior citizen must ride the bus for the monthly pass to be a better deal.

If f(x) = 6x – 4, what is f(x) when x = 8? a2 b16 c44 d52

1) prove that 731^3−631^3 is divisible by 100 2) prove that 99^3−74^3 is divisible by 25