A manufacturer has 600 litres of 12% acid solution. How many litres of 30% acid solution must be added
to it so that acid content in the resulting mixture will be more than 15% but less than 18%?
A roadside vegetable stand sells pumpins for $5 each and squashes for $3 each. One day they sold 6 more squuash than pumpkins, and their sales totaled $98. Write and solve a system of equations to find how many pumpkins and squash they sold