The spring starts out 22 cm long with nothing hanging on it.
Hanging 35 newtons of weight on it stretches the spring 1 meter.
Ellen is going to hang 250 grams of mass on the spring.
What's the weight of 250 grams of mass ?
Weight = (mass) x (acceleration of gravity in the place where the mass is) .
On Earth, the acceleration of gravity is 9.8 m/s² .
250 grams is 0.25 of a kilogram.
Weight of 250 grams = (0.25 kilogram) x (9.8 m/s²)
= (0.25 x 9.8) kg-m/s²
= 2.45 newtons .
2.45 newtons of weight is (2.45 / 35) of 35 newtons,
so it'll stretch the spring (2.45 / 35) of a meter.
2.45/35 = 0.07 of a meter = 7 centimeters.
The spring was 22 cm long with nothing hanging on it,
and the 250-gm weight stretched it 7 cm.
So with the weight hanging on it, it's (22 + 7) = 29 cm long.
