### Answer:

Time for some math. Let’s count how much 200 envelopes would cost, shall we? If 100 cost 70 cents, than 200 envelops should cost 70 times 2. Which is $1.40. Now, lets count how much the remaining 50 cost. If 100 cost 70 cents, 50 would cost exactly half of that. Which is 35 cents. Now let’s put the cost of 200 and 50 together. $1.40 plus 35 cents is $1.75. Voila!

It’s easy!