Answer:
5100 cm of wax will make 17 candles 
Step-by-step explanation:
 Each candle is 5 cm long, 4 cm wide, and 15 cm tall
to know the space they cover, we divide it with their volume and since they are in rectangular prism 
Volume is length x width x height 
5 x 4 x 15 = 20 x 15 = 300cm
1 candle = 300cm
what number of candle is represented as x 
 1 candle comprises of  300cm wax
x = 5100
300x = 5100 x 1 =5100
300x= 5100
x= 5100/300 = 17
5100 cm of wax will make 17 candles