Combine like terms:

2.4x + 6.2x + 5.4x = (2.4 + 6.2 + 5.4)x
= 14x

Then, the equation becomes:

14x + 8.3 + 1.7 = 66.7

Combine the constants:

14x + 10 = 66.7

Subtract 10 from both sides:

14x = 56.7

Divide by 14:

x = 4

Therefore, the solution to the equation is x = 4.