How is pumping "Air" into a bicycle make dW (delta work )negative , when in fact there is a increase in pressure and a slight increase in volume?
Depending on context and domain dependent convention, the work done is assumed in 2 different, opposite ways, with opposite signs.
Work done on a system $\Delta U = Q + W$, preferred by chemistry
versus
work done by a system $\Delta U = Q - W$, historically preferred by physics. It is used by the former way as well recently.

Speculatively said, physics way was defined during creation of theoretical background for thermal machines. Physicists may had been focusing on work done by machines.
Later chemists came, who invented their way, focusing on energy of systems.

As a prevention, it is always good to explicitly mention which way is used, to prevent confusion.
If applied, your pump is doing positive &quot;chemical&quot; work on the system=tyre, but the system=tyre does negative &quot;physical&quot; work on the pump. The textbook takes the convention of physics.


In an important sign convention, preferred in chemistry, work that adds to the internal energy of the system is counted as positive. On the other hand, for historical reasons, an oft-encountered sign convention, preferred in physics, is to consider work done by the system on its surroundings as positive.

Wikipedia - Work_(thermodynamics)