Solution,

Weight of body in liquid= 10N

Weight of displaced liquid= 2N

Weight of body in air=?

Using formula,

Weight of body in air= weight of body in liquid+ weight of displaced liquid

= 10+2

=12N

Upthrust= Weight of displaced liquid

= 2N

For mass of body,

Weight of body in air(W)=12N

Acceleration due to gravity= 10m/s^{2}

Mass of the body (m)=?

Using formula,

\begin{align*}m &=\frac{W}{g}\\ &= \frac{12}{10}\\&=1.2 \: kg. \end{align*}

Here,

Weight of stone in water= 9N

Weight of displaced water= 2N

Weight of stone in air=?

We know,

The weight of stone in air= Wt. of stone in water+ Wt. of displaced water

=9N +2N

=11N

Solution,

Upthrust of water=Weight of displaced water

=10N

Now,

Weight of stone in water=40N

Weight of displaced water =10N

Weight of stone in air=Wt. of stone in air+ Wt. of displaced water

=40N + 10N

= 50N

Here,

The weight of iron in air= 20N

The weight of iron in water= 12N

The weight of water displace by iron= ?

we know,

The weight of water displaced by iron=wt of iron in air- wt of iron in water

=20N-12N

=8N

The upthrust on the iron= weight of displaced water = 8N

Upthrust = Wt. of displaced water

∴8N=8N

Here,

Wt. of stone in water= 3N

Wt. of displaced water= 5N

we know that,

The wt. of stone in air= Wt. of stone in water+wt. of displaced water

=3N+ 5N

=8N

Again,

Upthrust= Weight in air- Weight in water

=8N-3N

=5N

Hence, upthrust of water is 5N and the weight of stone in air is 8N.

Here,

Weight of the object in air (W_{a}) =34N

Weight of the object in water (W_{w}) =10N

Upthrust = ?

Weight of the water displaced (W_{2}) =?

We know that,

Upthrust = W_{a}-W_{w}

= 34-10

= 24N

Again,

We know,

Upthrust (U) = Weight of the liquid displaced(W_{2})

∴ the weight of the liquid displaced =24N

Thus, upthrust on the body is 24N and weight of displaced fluid is 24N.