YOU ARE SMART YOU CAN DO THIS
Mass = density x volume
1st we need to get the volume
V = (25*10^-1) * (1.8) * (3)
V = 13.5 cm3
mass = 2.53 * 13.5
mass = 34.155 kg

It approximately the answer (17) if rounded
22.9 is the closest but not exact. It was probably rounded off.
I used the formula: leg^2+leg^2=hypotenuse^2
(You can use that formula for any right triangle.)