Pencils received : (+)
Number of pencils Kabilan has = 10
Number of pencils father gove = 6
= 16
Pencils given : (-)
Number of pencils gave to Senthil = 2
Number of pencils gave to Karthick = 3
Number of penciis gave to Sister = 8
= 13
Number of pencils left = Received - Given
= 16-13
Number of pencils left = 3                                              

(i) 0 + (-2345) = -2345
(ii) 23479 + (-23479) = 0
Therefore, additive inverse of 23479 is –23479

Let us add the intergers using number line
(i) 10 and –15

On the number line we first start at zero facing positive direction and move 10 steps forward, reaching 10. Then we move 15 steps backward to represent –15 and reach at –5. Thus, we get 10 + (–15) = –5.
(ii) –7 and –9

On the number line we first start at zero facing positive direction and move 7 steps backward, reaching –7. Then we move 9 steps backward to represent –9 and reach at –16. Thus, we get (–7) + (–9) = –16.

Since neither profit nor loss
Profit + Loss = 0
(ie) profit = -Loss
Profit earned from 1 notebook = Rs. 5
Profit earned from 20 notebooks = 20 x Rs. 5
= Rs. 100
Loss incurred by selling pens = Rs. 100 Loss
= −100
Loss for 1 pen = Rs. 2
loss = −2
Total number of pens sold = (−100) ÷ (−2)
= 50 pens.

(i) 70 - (-40)
= 70 + (additive inverse of−40)
= 70 + 40
= 110
(ii) (-20 )- (-12)
= (-20) + (additive inverse of (-12))
= (-20) + 12
= -8

(i) 

∴. 8 + (-12) = -4
(ii) 

∴ (-3) + (-5) = -8
(iii) (-100) + (-10) = -100-10 = -110
(iv) 20 + (-72) = 20 - 72 = -52
(v) 82 + (-75) = 82 - 75 = 7
(vi) -48 + (-15) = -48 - 15 =- 63
(vii) -225 + (-63) = 225 - 63 = -288

= -9

\(\frac{\mathrm{P}-\mathrm{Q}}{\mathrm{P}+\mathrm{Q}}=\frac{-15-5}{-15+5}=\frac{-20}{-10}=2\)

The level of the water in a pond decreases in a week  = -2 inches.
Level of water decreases in 6 weeks = 6 x -2 = -12 inches
The change in the level of the water over a period of 6 week is -12 inches

Let x be the number.
-17 + x = -19
x = -19 + 17
x =  -2
-2 should be added to -17 to get -19.