RATIO

(a+2):(a+5):b=3:4:7

(a+2)/(a+5)=3/4
(a+2)(4)=(a+5)(3)
4a+8 = 3a + 15
a = 7

Since (a+5) : b = 4:7 ,
therefore
(a+5) / b = 4/7
(7+5)(7) = 4b
(12)(7) = 4b
b=21

i.e. a=7 and b=21.

(a+2):(a+5)=3:4
(a+2)/(a+5)=9/12
(a+2)=9
a+5=12
a=7

(a+5):b=4:7
12/b=4/7
12/b=12/21
b=21