Can anyone simplify this for me. you!

If the tip varies directly with the number of guest which equation represents between the tip, t, and the number of guest, g?

Candice uses the function f(t)=t+100−−−−−−√ to model the number of students in her after-school program. the variable t represents days and f(t) represents the number of students. how many days does it take for there to be 15 students in her program? a. 225 days b. 125 days c. 325 days d. 115 days

The ratio of the ages (in years) of three children is 2: 4: 5. the sum of their ages is 33. what is the age of each child?