Find the 2 numbers whose sum is 51 and whose difference is 13

2 #'s whose sum is 51: x + y = 51
2 #'s whose difference is 13: x - y = 13

add the 2 equations: 2x = 64 ⇒ x = 32
using either equation find y: 32 + y = 51 ⇒ y = 19
Answer the 2 #'s are 32 and 19

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