A concave mirror has a radius of curvature of 48 cm .How far is an object from the mirror if an image is formed that Real and 3.0 times the size of the object 

$\text{f}=\frac{\text{R}}{\text{2}}=-\text{24cm}$

 Image is real and three times larger .

Hence u and v both are negative $\left|\text{V}\right|=3\left|4\right|$

$\text{u}=-\text{x}$

 $\text{then v}=-3\text{x}$

$\text{mirror formula }\frac{\text{1}}{\text{f}}=\frac{\text{1}}{\text{v}}+\frac{\text{1}}{\text{u}}$

$\frac{1}{-24}=\frac{-1}{3\text{x}}-\frac{\text{1}}{\text{x}}$

$\frac{-1}{24}=\frac{-1-3}{\text{3x}}$

$\frac{-1}{24}=\frac{-4}{\text{3x}}$

$\text{3x}=96$

$\text{x}=32\text{cm}$

Object distance should be 32cm