To solve it, convert 49% into a decimal, which would be 0.49 (you convert it to a decimal by moving the decimal twice to the left). Then, you multiply 0.49 to 15 which gives you the answer, 7.35.
If you wanted to make an equation like your question asks, you can set up a proportion and cross multiply. Since the question is asking for a part out of a whole (the whole is 15), your first fraction would be x/15. Then, for your next proportion, you would convert 49% to a fraction out of 100 which would be 49/100. Then, you would set the two fractions equal to one another so that the proportion looks like this: x/15=49/100
Then, you cross multiply (100*x=15*49) and you get 100x=735.
Finally, you solve for x and you get x= 7.35