Start by estimating the answer
One and three-fourths is a little less than 2. Half of 2 is 1, so half of 1 3/4 should be a little less than 1. This estimate is useful before you calculate because it gives you a size check. An answer larger than 1 3/4 cannot be right, and an answer such as 1 3/8 is too large to be half.
The answer 7/8 fits the estimate. Seven-eighths is just below one whole, and 1 3/4 is just below two wholes. Estimation does not replace the calculation, but it helps a child decide whether the final answer makes sense.