For a wonderful introduction or review of equations try these excellent Mobile puzzles.
Don Steward has posted this sum and product task (developed in the UK by Barbara Ball and Derek Ball) which would be ideal for a starter. For example find three expressions such that the sum is 5d+5 and the product is 30d2.
For another similar problem try What’s it Worth? from Nrich.
Try the Fido Puzzle!
or a little mind reading – try Regifting Robin (turn the sound on).
Can you work out what is going on?