Cardio and weights don’t go against each other due to the different benefits they give to your body.

Cardio works on your heart lungs (to keep them strong fit) and increasses your metabolism, so you’ve higher fat-burning capacity to burn off excess body fat, to lose weight.

This article on cardio explains it all:

Weights boost your muscle growth and benefit you in several ways:

1. Strengthen your muscle hence provide your body with stronger support

2. Build up your muscle; the more muscle you’ve, the higher your metabolism and the more calories you burn, to lose weight (due to the fact that muscle is metabolically active; it raises your resting metabolic rate [the rate you burn off calories even while resting])

3. Muscle also burns off fat faster

In fact, it’s really good if you can cardio and then do weights, one after another.

I don’t think so. It might make the weights a bit more aerobic like because your heart rate will be up from the cardio.
I think it might be counter productive if you did heavy lifting because of the fatigue factor. You may not be able to go as heavy as you could have.

Hi Nat

Depends on what you’re trying to achieve. If you’re doing aerobics for that 45 minutes and then 15 of weights then that should be fine. The aerobics is a weight loss program and the weights will be to tone up the loose skin.
Take care