Your equation is 150/100 = x/400. Reduce to get 3/2 = x/400. Cross multiply to get 2x = 1200. Divide both sides by 2 to get x = 600.
Be aware: I have not done this kind before. I dont know what tablets mean, But if its like what im use to, 100% of 400 is 400. So 150% of 400 should be 600. So it should be 600 tablets.
