Formula for speed = distance/ time
S = 7/.9 = 7.77 miles per hour or 8 mph if you round up.
Let the amount of stamps Mari has be “m”. Since Carlos has 5 more stamps than Mari, Carlos will have 5+m stamps. Amanda has three times as many stamps as Carlos so that will be 3(5+m)=15+3m.
m+(5+m)+(15+3m)=100
5m+20=100
5m=80
m=16
Mari=16
Carlos=16+5=21
Amanda=15+48=63
