To solve this proportion, we can first convert the division into multiplication by taking the reciprocal of the second fraction:

2.5 ÷ 13.5 = x ÷ 3/5
2.5 ÷ 13.5 = x * 5/3

Next, we can simplify the left side of the equation:

2.5 ÷ 13.5 = 0.185

Now we can solve for x by multiplying both sides by 3/5:

0.185 = x * 5/3
0.185 * 3/5 = x
0.111 = x

Therefore, x = 0.111.