Discrepancy between the formulas and the exercise solution

I think there is some discrepancy between the formulas given for pooled sample variance and the standard error formula given in the confidence interval formula. Given the confidence interval formula, the pooled sample variances must be divided by the respected sample size and then be squared root. However, in the exercise solution, you just took a square root of the pooled sample variance. I am confused. I would appreciate any clarification.

Thanks