PAULA ,SIMON AND RANDY COLLECTED INSECTS FOR THEIR SCIENCE PROJECT. AT THE END OF THE FIRST WEEK PAULA AND RANDY TOGETHER HAD 89 INSECTS, RANDY AND SIMON TOGETHER HAD 80 INSECTS, PAULA AND SIMON HAD TOGETHER HAD 85. HOW MANY DID EACH HAVE ALONE?
P + R = 89
R + S = 80
P + S = 85
combine the first two equations by subtraction
P - S = 9
add that to the third
2 P = 94
P = 47
S = P-9 = 38
R = 80 - S = 42
check that
P+R = 47+42 = 89 yes
R+s = 42+38 = 80 yes
P+S = 47+38 = 85 yes