So when you solve something like this you want to try to represent all the boxes using one variable. The question tells you that box A weighs 2.6kg more than box B. So the mathematical way to represent that is A=2.6+B. Then it tells you that Box B weighs 4.5kg more than box C (B= 4.5+C). However, in order to represent all the boxes using one variable, you need to change the equation so that box C is represented in terms of B. (To do that you subtract B from both sides giving you 0=4.5+ C -B. Then subtract C from both sides of the equation giving you -C= 4.5-B. Then you multiply both sides by -1 so that your variables are positive. That gives you C=B-4.5).

Now you have everything represented in terms of B. 81.05=A+B+C can be written as 81.05= 2.6+B +B +B-4.5 (see above equations to see how I did that). Then it is just a matter of getting B all by itself.

Once you have a value for B, you can plug it into the equations for A and C to get values for those variables.

Hope that makes it more clear as to HOW you get the answers.

Box A – 30.25 kgs. B – 27.65 kgs. C – 23.15 kgs. Can’t do it yourself ????????????????? Very poor in Maths. Work hard.