Practice problems on adding integers, including sums of two integers, three integers, and using properties of addition like commutative and additive inverse.

The sum is $\boxed{-5}$.

b)

The sum is $\boxed{0}$.

c)

The sum is $\boxed{40}$.

d)

The sum is $\boxed{45}$.

e)

The sum is $\boxed{-54}$.

2. Add:

a)

The sum is $\boxed{-190}$.

b)

The sum is $\boxed{6}$.

c)

The sum is $\boxed{-110}$.

d)

The sum is $\boxed{7}$.

3. Fill in the blanks:

a)

The blank is $\boxed{-16}$.

b)

The blank is $\boxed{54}$.

c)

The blank is $\boxed{0}$.

d)

The blank is $\boxed{-41}$.

e)

The blank is $\boxed{-36}$.

f)

The blank is $\boxed{-24}$.

g)

The blank is $\boxed{-24}$.

4. Add:

a)

The additive inverse of $-31$ is 31.

The sum is $\boxed{0}$.

b)

The sum is $\boxed{-34}$.

5. Simplify by applying commutative and associative properties:

a)

$a + (b + c) = (a + b) + c$.

The simplified value is $\boxed{75}$.

b)

$a + (b + c) = (a + b) + c$.

The simplified value is $\boxed{80}$.

c)

$(a + b) + c = a + (b + c)$.

The simplified value is $\boxed{50}$.

d)

$(a + b) + c = a + (b + c)$.

The simplified value is $\boxed{-21}$.

6.

Earnings last week $= ₹4,200$
Earnings this week $= ₹10,800$
Combined earnings $= ₹4,200 + ₹10,800 = ₹15,000$

Since the shop earned money, it is a profit.
The combined earnings for the two weeks are $\boxed{₹15,000}$. It is a profit.

7.

Initial height $= +415 \text{ metres}$

Change in height $= -120 \text{ metres}$ (negative indicates a decrease in height)

New height $= \text{Initial height} + \text{Change in height}$

Since the new height ($295 \text{ m}$) is less than the initial height ($415 \text{ m}$), the balloon came down.

A hot-air balloon rises because the air inside the balloon is heated, making it less dense than the cooler air outside. This difference in density creates an upward buoyant force that lifts the balloon.

The new height is $\boxed{295 \text{ metres}}$. The balloon came down from the initial height. A hot-air balloon rises because the air inside it is heated, making it less dense than the surrounding cooler air, which generates an upward buoyant force.