How to divide monomials

Two times a number plus three times another number equals 4. three times the first number plus four times the other number is 7. find the numbers

How many kilograms of a 5% salt solution and how many kilograms of a 15% salt solution must be mixed together to make 45kg of an 8% salt solution?

Ineed your ! i was to turn this into pond first thing i gotta do is outline the inside with this plastic how big should i cut the plastic the height: 10 1/2” the length: 40” the width: 12” me !