Answer
The concentration of casein in that low-fat milk is equal to 6.2% (m/v)
Work Step by Step
1. Write the concentration expression:
$Concentration \space (m/v) = \frac{mass \space of \space solute \space (g)}{volume \space of \space solution \space (mL)} \times 100 \%$
2. Substitute the values, and calculate the concentration:
$Concentration \space (m/v) = \frac{7.5 \space g }{120 \space mL} \times 100 \% = 6.2\% \space (m/v)$