We can take adult ticket as x and senior ticket as y.
Now we will form two equations
x + y = 140
13x + 10y = 1664
This system of equations we will solve using Gaussian algorithm (gradual elimination of the variables)
We will multiply first equation with (-10) and get
-10x-10y=-1400 Than we will add to second equation and get
3x=264 => x=264/3=88 => x=88
Now we will replace x in the first equatin before multiplying and get
88+ =140 => y= 140-88= 52 => y=52
adult tickets x=88 and senior tickets y=52
Good luck!!!