Difference between 2 lbs(pound) values

Difference between 2 lbs(pound) values

I need a suggestion in finding difference between two lbs(pound) values. I
tried in 2 ways,
First way,
var pound1 = 151.10;
var pound2 = 142.19;
var finalPoundValue = (151.10 - 142.19);
// result 8.91 -> 8 Pounds 91 Ounce
Second way,
var value1 = 151.10;
var value2 = 142.19;
var poundDiff = (151 - 142);
var ounceDiff = (10 - 19);
// result 9 Pounds -9 Ounce
but, don't know which one is the right way to find difference between
pound values. Or any other best method available to solve this problem..?