5.1%w/v is 5.1g apple juice concentrate per 100ml product.
We’re assuming the corrected Brix equates directly to soluble solids, i.e. the apple juice concentrate contains 70g of soluble solids per 100g, so 5.1g contains 70*(5.1/100) = 3.57g of soluble solids.
100ml of the reconstituted apple juice at 11.5 Brix contains 11.5g solube solids per 100g, so 3.57g is equivalent to 100*(3.57/11.5) = 31.04g of reconstituted juice per 100ml, i.e. 31.04%w/v.
Whether the aloe counts towards the overall juice content is going to be a question of local regulatory interpretation – the parts of aloe used for pulp aren’t a fruit, so over here they wouldn’t count towards fruit content.
Nonetheless if we assume that you are somewhere that would treat this as part of the fruit juice content, you first work out how much of the pulp is “pulp”, rather than dice (I’m assuming that it only counts if it’s in liquid/puree form?):
42% of 6g is 2.52g, so the portion of the aloe that isn’t solid dice is 6-2.52 = 3.48g.
3.48g in 1L is 0.348g per 100ml, i.e. 0.348%w/v.
If you add this to your apple you get a total juice content of 31.04+0.348 = 31.39g per 100ml, or 31.4% w/v (assuming the local labelling rules permit it to be rounded this way – otherwise you’d need to round down to 31.3%).