here is a couple of useful formula to use when you get problems like this.
[tex]Molarity= \frac{moles}{Liters} [/tex] -----> [tex]moles= (Molarity) x (Liters)[/tex]
since they are asking for moles, we are using the one on the right.
Molarity= 1.8 M
Liters= 2.90 L
moles= (1.8 M) x (2.90 L)= 5.2 moles of NaOH
