Alright, to start this question we know that 1.25 m/s = 25 N, and we want to find out the acceleration of a 35 N force. What we're going to do for now is focus on the first equation to get a cleaner equation. To help us out a bit, I'm going to change the variables of both parts of the equation, so m/s will be abbreviated as m, and N will be n.
We know that 1.25m=25n, so we can take that information and transform it a bit more. We know that 1.25 can be shown with the fraction 5/4, so we'll use that for now, so 5/4m=25n. now, we can multiply both sides by 4 to get 5m=100n, and then divide both sides by 5 to get a cleaner answer. Now we know that 1m=20n!
Now that we know that 1m=20n, we can divide the 35n in the second part of the equation to see what the acceleration of 35n will be! So 35/25 simplifies to 1.75, which means 35 Newtons of force will create an acceleration of 1.75 m/s, which should be your answer!