Answer:
Sydney worked for 4 hours and Riley worked for 9.
Explanation:
Riley worked 5 more hours than Sydney we can add the amount of shirts that Riley can do per hour (10) times the extra amounts of hours that the problems says she does (5).
The equation:
15x+10x+50=150
Solving it:
25x+50=150
25x=100
x=4.
Sydney worked for 4 hours ironing shirts and since Riley worked for 5 more hours than Sydney, 4+5=9. Riley worked for 9 total hours.