5. Xiaopang went to the supermarket to buy 4 boxes of milk for 26 yuan, buying 6 boxes of such milk would cost $\qquad$ yuan
【Analysis】 $\frac{26}{4} \times 6=39$ yuan 【Consider two boxes of milk as one portion, one portion of milk is 13 yuan; thus, 6 boxes, or 3 portions of milk, are 39 yuan】