Answer
$$\approx 1.87 \times 10^{4} .
$$
Work Step by Step
we suppose a number of weight lift repetitions denoted by $ N. $
Then $$N m g h=Q, $$ or (by using Eq. $18-12$ and discussion preceding it) we reached to:
$$
N=\frac{Q}{m g h}=\frac{(3500 \mathrm{Cal})(4186 \mathrm{J} / \mathrm{Cal})}{(80.0 \mathrm{kg})\left(9.80 \mathrm{m} / \mathrm{s}^{2}\right)(1.00 \mathrm{m})} \approx 1.87 \times 10^{4} .
$$
