Step-by-step explanation:
Molarity is defined as the number of moles divided by volume of solution in liter.
Mathematically, Molarity =

Since, it is given that molarity is 0.75 M and volume is 1.25 liter. Therefore, calculate the number of moles as follows.
Molarity =

Number of moles =

=

= 0.937 mol
Thus, we can conclude that number of moles of solute are present in 1.25 l of a 0.75m nano3 solution is 0.937 mol.