Time p.m. Mass (g)

1:00 2.5754
1:08 2.5621
1:15 2.5615
1:24 2.5609
1:31 ?

How do I predict the mass at 1:31 of this solid that is weighed every 5 minutes while drying?

I can't draw a graph on the board. Take a piece of graph paper and plot the tme on one axis versus the mass on the other, draw a line connecting the points, then extrapolate from 1:24 to 1:31.