Multi-step word problems
Name the quantity being asked for, list what you know in matching units, then work towards it in stages.
A worked example
A job pays a $20 call-out fee plus $15 an hour, so 5 hours of work comes to 20 + 15 x 5 = $95.
The mistake people actually make
Convert times to a single unit before dividing, so 1 h 30 min becomes 1.5 h. When whole items must be bought, round up rather than to the nearest.