The difference of 25 and a number added to triple another number
The phrase a number means an arbitrary variable, let's call it x:
x
The difference of 25 and a number means we subtract x from 25:
25 - x
The phrase another number means a different arbitrary variable, let's call it y:
y
Triple another number means we multiply y by 3:
3y
The phrase added to means we add 25 - x to 3y
25 - x + 3y
The phrase a number means an arbitrary variable, let's call it x:
x
The difference of 25 and a number means we subtract x from 25:
25 - x
The phrase another number means a different arbitrary variable, let's call it y:
y
Triple another number means we multiply y by 3:
3y
The phrase added to means we add 25 - x to 3y
25 - x + 3y