Răspuns :
840-642=198 (c)
840-553=287 (a)
287+198=485
840-485=355 (b)
a+b+c=287+355+198=840
840-553=287 (a)
287+198=485
840-485=355 (b)
a+b+c=287+355+198=840
840-642=198 C
840-553=287 A
287+198=485
840-485=355 B
a+b+c=287+355+198=840
840-553=287 A
287+198=485
840-485=355 B
a+b+c=287+355+198=840