Pg 15 num 46 Target Cost

I assume that you are referring to the BPP Revision Kit, but please do say in future which book you are using. The target cost is 100/125 x $120 = $96. The variable costs are $46 per unit, and so to achieve the target cost they have to reduce the fixed costs to 96 - 46 = $50 per unit. The total budgeted fixed costs are 10,000 x $60 = $60,000. So to end up with a fixed cost of $50 per unit, they need to produce 60,000/50 = 12,000 units.

Yes it is in BPP sir, forgot to mention it. Why 100/125 *120?

Because the mark up is 25% of the cost. Therefore the selling price is 125% of the cost.