let 'x' be the number that needs to be added to the difference of 3.14 and 1.674 to get 9 that is

x + (3.14 - 1.674) = 9

x = 9 - (3.14 - 1.674)

x = 9 - 3.14 + 1.674

x = 7.534

the answer is 7.534.