What is the volume of this prism? !

The rows and columns of lattice points in a three-by-three square array are evenly spaced one unit apart. how many distinct triangles with at least one side of length 2 units can be drawn using three lattice points for the vertices?

The? half-life of a radioactive substance is 20 years. if you start with some amount of this? substance, what fraction will remain in 120 ? years

Can some one explain how to slove specifically, what is the value of x? 0.9(x+1.4)-2.3+0.1x=1.6 enter the answer as a decimal in the box. x= ?