When 100g of liquid A at 100⁰C is added to 50g of a liquid B at temperature 75⁰C, the temperature of the mixture becomes 90⁰C. Then the ratio of specific heats of liquid A to liquid B is 

Energy lost by liquid = Energy given by liquid
Mass $\times$ specific heat $\times$  temperature = mass $\times$  specific heat $\times$  temperature
$\Rightarrow 100\times C_A\times [100-90]=50\times C_B\times [90-75]$
$\Rightarrow 100\times 10\times C_A=50\times C_B\times 15$
$\Rightarrow C_A=\frac{50\times 15}{100\times 10}{C}_B$
$\Rightarrow C_A=\frac{3}{4}{C}_B$