If for each pound there are 16 ounces, then we can expressed this as;
1 pound = 16ounces
For us to calculate the total number of ounces in 3pounds, we can say;
Z ounces = 3pounds
Solving both equalities as shown;
1 pound = 16ounces
3 pounds = Z ounces
Cross multiply
1 * Z = 16 * 3
3 = 16Z
Divide both sides by 16
3/16 = 16Z/16
3/16 = Z
Z = 3/16
Hence the total ounces in 3pounds is 3/16 ounces