2/5 - 4/5 + -9/10 =

, will mark brainliest for answer with an explanation

Two customers went to a post office. first customer paid $12 for 14 and 5 envelopes the second paid 24.80 for 10 postcards and 15 envelopes. what is cost of each envelope?

What is the total surface area of this square pyramid?

If i purchase a product for $79.99 and two accessories for 9.99 and 7.00 how much will i owe after taxes applies 8.75%