Ikeep messing this up for #13 i got (1/19, 35/38) and for #15 i got (2,-1) both of which i know are wrong, someone me understand what i did wrong?

2x  + y = x/2 + 1  multiply  this by -4:-
-8x - 4y = -2x - 4
4y         = 2x       Adding:-

-8x = -4
x = 1/2

Substitute in 4y = 2x:-

4y = 2*1/2

y = 1/4 

Answer ( 1/2, 1/4)

I’m not absolutely sure but i think it’s 7x6x5x4x3x2=5040 because as the first character you can take any of the 7 given then you are left with 5 then 6 then 4 etc.

The answer would be 13.5 minutes.