Answer:
A+B+C=28
Explanation:
let
A-B=2 -----1 EQUATION
B-C=7-------2
A+C=17------3
FROM 1 AND 2
A-C=9---------4
FROM 2 AND 3
A+B=24 -------5
FROM 3 AND 4
2A=26
A=13 SUBSTITUTING A=13 IN 5
WE GET B=11 SUBSTITUTING IT IN 2
WE GET C=4
NOW
A+B+C=13+11+4=28