Answer: 5
Step-by-step explanation: To solve for <em>k</em> in the given proportion, we use the means-extremes property. The product of the extremes, (k)(18), equals the product of the means, (6)(15).
So we have (k)(18) or 18k = (6)(15) or 90.
Now we have the equation 18k = 90.
Dividing both sides by 18, <em>k = 5</em>.
It's a good idea to check the answer in these types of problems so if we plug a 5 back in for <em>k</em> in the original proportion, we have
which is a true statement since 15/18 reduces to 5/6.