Rewrite math problems without zero or a negative exponent

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?

How can constraints be used to model a real-world situation?

Divide. –4.2 ÷ 6 = a –0.7 b 0.7 c –7 d 7 me