To find out how far Grace ran in 1.5 hours, we first need to determine her running speed.
She ran a 26-mile marathon in 4 hours, so her speed is:
\[ \text{Speed} = \frac{\text{Distance}}{\text{Time}} = \frac{26 \text{ miles}}{4 \text{ hours}} = 6.5 \text{ miles per hour} \]
Now, we can use this speed to find out how far she ran in 1.5 hours:
\[ \text{Distance} = \text{Speed} \times \text{Time} = 6.5 \text{ miles per hour} \times 1.5 \text{ hours} = 9.75 \text{ miles} \]
So, Grace ran 9.75 miles in 1.5 hours.
The correct response is 9.75 miles.