If work is done by a body against a force,is the work considered positive or negative?

$A$ block of mass $M$ is pulled a distance $x$ on a horizontal table. The work done by the weight (gravitational force) is:

$A$ body of mass $3\, kg$ is under a constant force which causes a displacement $s$ in metres in it,given by the relation $s = \frac{1}{3}t^2$,where $t$ is in seconds. Work done by the force in $2$ seconds is

$A$ force $\vec{F} = 6\hat{i} + 2\hat{j} - 3\hat{k}$ acts on a particle,causing a displacement $\vec{S} = 2\hat{i} - 3\hat{j} + x\hat{k}$. If the work done during this displacement is zero,find the value of $x$.

$A$ particle moves from position $\vec{r_1} = 3\,\hat{i} + 2\,\hat{j} - 6\,\hat{k}$ to position $\vec{r_2} = 14\,\hat{i} + 13\,\hat{j} + 9\,\hat{k}$ under the influence of a force $\vec{F} = 4\,\hat{i} + \hat{j} + 3\,\hat{k}$. Find the work done in $J$.

$A$ particle of mass $100 \ g$ is projected vertically upwards with a speed of $5 \ m/s$. What is the work done by the force of gravity during the time the particle returns to the starting point? (in $J$)