What work is done by a force (in newtons) F = 3.1xi + 3.1j, with x in meters, that moves a particle from a position r1 = 2.1i + 2.5j to r2 = - -4.9i -3.9j?

Work is the dot product of Force and displacement.

Change in displacement is r2 minus r1. I will be happy to critique your work on this.

Rememeber dot product is a scalar, the sum of i component times i component plus j component times j component etc.