Answer:
x=3
Step-by-step explanation:
6 10
---------- = ------------
6+x 15
using cross products
6 * 15 = 10 * (6+x)
90 = 60+10x
subtract 60 from each side
90-60 = 60+10x-60
30 = 10x
divide by 10
30/10 = 10x/10
3=x
