Answer:
In an electrophilic aromatic substitution (Friedel Crafts alkylation) first in the monoalkylation of the 1,4-dimethoxybenzenethe the methoxy groups redirects the substitution for ortho-para positions with respect to the electrophile that is going to enter (alkyl group) this is due to the increase in electron density in that position, that is , to the inductive effect.
According to the second incoming alkyl group there would be 3 positions available, from which it will choose the meta position in relation to the second methoxy group, since the alkyl group is a weak activator of the ortho meta positions and coincides with the position to which it redirects the second methoxy group.