The domestic postage rate for first-class letters weighing 12 oz or less is $0.37 for the first ounce and $0.23 for each additional ounce or part of an ounce. which of the following is a correct cost?

Hello!

To find the cost of 12 oz:

first oz = $0.37
Every oz after = $0.23

12 - 1 = 11
First oz = $0.37

11 × .23 = 2.53

2.53 + 0.37 = 2.9

A 12 oz package in first class would cost $2.90. 

Hope I helped you! :) 

PS. Next time please add the answer choices! :)

Aand b are correctly balanced reactions. they have the same number of atoms in both sides of the reaction