Let x be the amount of salary spent on transport and saved.

80% x = $1120, so x = $1400

Including food, he would have $1400+$350 = $1750

This is 70% of his salary.

So his salary is 1750 * 100 / 70 = 2500

Therefore % of salary spent on food = 350/2500 * 100 = 14% #

Thanks for the help.