Suppose Xiaoqing's father's salary this month is X yuan, then120+x-984 = 636; Suppose you buy x kilograms of rice, then 4.4x+3.2x20 = 90.4, x = 6；; If X parts are produced every day on average in 4 days, then 5×1200+4x =11500, x =1375; Assuming that car B travels x kilometers per hour, then 6x=40×7.5, x = 50 Assuming that there are x cars with a load of 5 stews, then 3x8+5x = 54, then X = 6；; Let each box of pears weigh x kilograms, then 28×25+24x= 1 180, then x=20.