Question

1)a = 5 supra 7 - 3supra 7 si b = 1supra 3 +3supra7
2)

Answer 1

a=2/7;
b=1/3+3/7⇒b=7/21+9/21=16/21;
⇒[a+b]/2
⇒[2/7+16/21]/2
⇒[6/21+16/21]/2
⇒22/21·1/2
⇒11/21·1/1⇒11/21;