1) Mrs Lee bought x kg of crabs for $140. Write down an expression, in terms of x for the cost of 1 kg of crabs.
2) She bought some fish with $140. She received 3 kg more fish than crabs. Write down an expression, in terms of x for the cost of 1 kg of fish.
3) The cost of 1 kg of fish is $15 less than the cost of 1 kg of crab. Write down an equation in terms of x and show that it reduces to 3x^2+9x-84=0.
4) Solve the equation 3x^2+9x-84=0.
5) How many of kilograms of fish and crabs did she buy?