Since a and b are in the ratio 7:5

Then, Let a = 7k and b = 5k %3D

Then c = 2a = 2 x 7k = 14k %3D

d = 3b = 3 x 5k = 15k %3D

– c:d = 14:15

%3D

– ac : bd = 14 x 7:15 x 5 = 98:75

a:b = 7:5

c:d = 2a:3b

ac:bd = ?

As a:b = 7:5

we get a=7 and b=5

So, c:d = 2*7:3*5

or, c:d = 14:15

Therefore, c = 14 and d = 15

ac or, a*c = 7*14=98

and bd or, b*d = 5*15=75

So, ac:bd = 98:75  (answer)