I represented the algebraic structure accurately, kept each transformation valid and checked the result by substitution, graph or equivalent reasoning.
Even Better If (EBI)
I will show the missing inverse operation or algebraic step, keep signs and brackets accurate and test the result in the original relationship.
Stretch and deep challenge
Stretch: A taxi charges £3.50 plus £1.80 per mile. Find miles travelled for a £21.50 fare.
Deep challenge: A rectangle's perimeter is 38 cm and its length is 3 cm more than width. Find dimensions.