(a) The ratio is:
[tex]\frac{\text{ number of cups of flour}}{\text{ number of pancakes}}[/tex](b) This ratio is equal to:
[tex]\begin{gathered} \frac{\text{ number of cups of flour}}{\text{ number of pancakes}}=\frac{2}{10} \\ S\text{implifying} \\ \frac{\text{ number of cups of flour}}{\text{ number of pancakes}}=\frac{1}{5} \end{gathered}[/tex](c) Isolating "number of cups of flour":
[tex]\text{ number of cups of flour}=\frac{1}{5}\cdot\text{number of pancakes}[/tex]Isolating "number of pancakes":
[tex]5\cdot\text{ number of cups of flour}=\text{ number of pancakes}[/tex]The number of pancakes made is 5 times the amount of cups of flour needed.
The amount of cups of flour needed is 1/5 of the number of pancakes made.
(d) Substituting with "number of pancakes" = 70, we get:
[tex]\begin{gathered} \text{ number of cups of flour}=\frac{1}{5}\cdot\text{7}0 \\ \text{ number of cups of flour}=14 \end{gathered}[/tex]She will have to use 14 cups of flour