Answer :
Actually you have 2 coefficients here: 3/8 and 3/4.
(3/8)d + (3/4) is the same as (3/8)d + (2)(3/8), so this can be factored into
(3/8) [ d + 2 ]
(3/8)d + (3/4) is the same as (3/8)d + (2)(3/8), so this can be factored into
(3/8) [ d + 2 ]