We need to write down two equation here. Lets write the adult price as letter A and student price as letter S.
First Bus: 2A+5S=77.
Second Bus: 2A+7S=95.
There are many different ways to do this, I'll but the standard way here now and put the way I'd do it myself at the end of my comment:
Simultaneous Equations: take the first bus away from the second. Subtract the LHS's and the RHS's like so:
2A+7S-(2S+5S)=95-77
2S=18
S=9.
Then substitute S=9 into one of your equations:
2A+5S=77
2A+(5*9)=77
2A+45=77
2A=77-49
2A=28
A=14
Now put S and A back into the other equation to check you are right:
2A+7S=95
2(14)+7(9)=95
28+63=95
95=95 We are correct.
Answers: Adult price $14, Student Price $9.
Extra: My way of doing it:
Seeing that we have 2A and at least 5S in each, take the second bus equation and split the 7S into 5S and 2S.
2A+7S=95
(2A+5S)+2S=95
We can see that the bit in the brackets is our first bus equation, which =77.
77+2S=95
2S=95-77
2S=18
S=9
Then do the rest as normal, just saves you trying to subtract both sides in your head, but this will only work if you already have one equation in your second one.