In a math exam, Zach, Wendy, and Lee have an average score 91. Wendy, Lee and Chen have an average score 89. Zach and Chen have an average score 95. What is Zach's score?

98

Step-by-step explanation:

Z as Zach; W as Wendy; L as Lee; C as Chen

We know that average score of Z,W, and L is 91, so:

(z + w + l)/3 = 91

z + w + l = 273

Average score W, L, C = 89, so:

(w + l + c)/3 = 89

w + l + c = 267

We take both:

(z + w + l) – (w + l + c) = 273 – 267

z – c = 6

Average score Z and C = 95

(z + c)/2 = 95

z + c = 190

(z + c) – (z – c) = 184

2c = 184

c = 92

z + c = 190

z + 92 = 190

z = 98

So, Zachs score is 98