the ratio is 1:2 so 5 is half of 10 and if 10 becomes 30 it’s tripled so you would then have to triple 5 getting 15 , i hope this is right if not i’m sorry
Using proportions part/whole, percent/100 you put the 40 in the percent spot and the 2 in the part spot cross multiply and divide so 2 x 100 divided by 40 and you get 5
