I will assume the following based on the visible text and common chemistry problems:

Okay, Gilbert, this looks like a chemistry problem involving concentration and moles, likely from a titration experiment given the context of solutions A and B. The image is a bit faint, but I can make out the key information.

I will assume the following based on the visible text and common chemistry problems:

• The concentration of solution A ($C_A$) is $0.02 \text{ M}$ (from the faint text at the top).
• $25 \text{ cm}^3$ of solution B reacted with $2.78 \text{ cm}^3$ of solution A. This means the "2.78" refers to the volume of A used.
• The reaction between A and B has a $1:1$ mole