anyway. write the percentages as decimals. (remember, "percentage" means divided by 100, so 25% = 25/100 = 0.25, for example).
Let be the amount of juice in brand A (we can convert to percentage when finished)
we have 8 gal of brand B where 48% = 0.48 of it is juice. thus, the amount of juice in B that is juice is (0.48)8 = 3.84
similarly, we want, 0.3(17) = 5.1 gal of the mixture to be juice.
again, similarly, the amount of juice in A is given by
thus we have:
now solve for x and you can get the rest i think