Question

find the value of 3x+3y if x+y=20and x-y=-4.
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Answer 1

Answer:

Method 1: If (x+y) = 20

Then,

= 3x+3y

= 3(x+y)

= 3(20)

= 60

Method 2: Given,

(x+y) = 20 ....(i)

(x-y) = -4 ....(ii)

Substituting the value of x from eq i,

x = 20-y

Value of y from eq ii,

= 20-y-y = -4

= 20-2y = -4

= 24 = 2y

= y = 12

Value of x = (x+12) = 20

= x = 8

= 3x+3y

= 3*8 + 3*12

= 24+36

= 60

Hope this helps.