if a 150 lb person can burn 410 calories /hour while bicycling 12 mi/h

Question

What rate would a 120 lb person burn calories while bicycling 12 mi/h?

can some one explain this to me how to solve these kind of problems

One has to assume some relationship with caloric burning rate and weight.

Lets assume it is proportional (in reality I doubt if it is).

150/120 = 410/x

solve for x.

150/120=410/x
150x=120 x 410
150x = 49200

if i divid 150 into the 49200 i would get 328

rate would be
328cal/h
am i correct