Three cups and four plates cost $87. Two cups and five plates cost $93. Then what is the cost of one cup?
3 c + 4 p = 87 ... multiplying by 2 ... A) 6 c + 8 p = 174
2 c + 5 p = 93 ... multiplying by 3 ... B) 6 c + 15 p = 279
subtracting A) from B) ... 7 p = 105
solve for p , then substitute back to find c