Respuesta :

First get rid of the fractions by multiplying by the LCM of 2, 3, and 4. So in this case 12. 

120 - 6(n-1) - 4(n-2) = 3(n-3)

Then distribute the coefficients and simplify 

120 - 6n + 6 - 4n + 8 = 3n - 9

134 - 10n = 3n - 9
143 = 13n
n = 11