how can i get accurate results of these operations?

Question

i have a token swap contract that does simple operation, TokenA is 150% of value of TokenB

so if i swap 5 of TokenA i get 7.5 of TokenB

the problem is that solidity doesn't accept floating point numbers so how do i get accurate result of the following operation

        uint256 exchangeAmount = uint256(((100 / ratio) * 100)) * amount) / 100
    ) - fees;

if 100/ratio is less then 1, solidty will automatically round that value to zero and i would get erroneous values, how do i solve this problem?