Question

100 envelopes cost $0.70 how much would it be for 250

Answer 1

It costs 1.75$ for 250 envelopes. each one of the envelopes cost 0.007$

Answer 2

If 100 envelopes cost 0.70, this means that the cost of one envelope is $0.70 ÷ 100, which is $0.007.
The cost of 250 envelopes would then be 0.007 × 250, which is $1.75