How do I solve 6/15=2/c

I would say cross multiply. That would give you 30 = 6c, making c = 5.

6 2 - - - - = 0 15 c Step 2 : 2 Simplify - 5 Equation at the end of step 2 : 2 2 - - - = 0 5 c Step 3 : 2 2 Simplify - - - 5 c Calculating the Least Common Multiple : 3.1 Find the Least Common Multiple The left denominator is : 5 The right denominator is : c