To evaluate higher roots that are not perfect powers, we use a calculator and then round the result.

For example, to approximate $\sqrt[3]{49}$: Step 1: Use the calculator's $\sqrt[y]{x}$ key to find the cube root. The display shows $3.659305710\dots$ Step 2: Round to two decimal places. The hundredths digit is $5$ and the next digit is $9$. Since $9 \geq 5$, we round up to get $3.66$. Thus, $\sqrt[3]{49} \approx 3.66$.

Similarly, to approximate $\sqrt[4]{51}$: Step 1: Use the calculator to find the fourth root. The display shows $2.6723451177\dots$ Step 2: Round to two decimal places. The hundredths digit is $7$ and the next digit is $2$. Since $2 < 5$, the digit stays the same, giving $2.67$. Thus, $\sqrt[4]{51} \approx 2.67$.