Answer :

First, determine what 50% of 42 is. 
42 x 0.50 = 21 (Note: 0.50 is 50% in decimal form).
Then, add 50% of 42 (Which is 21) to 42. 
42 + 21 = 63
So, if 42 customers increased by 50%, there are now 63 customers. 
Hope that helps!!
First you find half of 42, which is 21, then add 21 to 42, which is 63. I hope that helped!