answer all questions for brainlist and 30 points

Answer:
All answers in explanation...
Step-by-step explanation:
16: S = more shoes than Ruben 10+s
17: M = money spent on dinner M-5
18: M = Mary's ringtones 3 + 2M
19: C = cost S= shoe rental C = S + (3*4)
20: C= cost C + 12.75 + (4 * 3)
Hope this helps :)