Question

If 2a + 3b + 4c = 35 and
3a + 5b + 7c = 30 then find a + b + c = ?


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Answer 1

Given Equation is 2a + 3b + 4c = 35   ----- (1)

Given Equation is 3a + 5b + 7c = 30    ----- (2)

On subtracting (2) - (1), we get

= > 3a + 5b + 7c - 2a - 3b - 4c = 30 - 35

= > a + 2b + 3c = - 5    ------ (3)

On subtracting (1) - (3), we get

= > 2a + 3b + 4c - a - 2b - 3c = 35 - (-5)

= > a + b + c = 40.

Hope it helps!

Answer 2

There are 2 equation and 3 variables, so if we try to make new equations or values of variables, it will be a wastage of time. We can never get the values untill there will be 3 equation.






So,


2a + 3b + 4c = 35 ----: ( 1 )
3a + 5b + 7c = 30 ----: ( 2 )




Multiply by 2 on ( 1 ),

=> 2[ 2a + 3b + 4c = 35 ]
=> 4a + 6b + 8c = 70



Subtract ( 2 ),



=> 4a + 6b + 8c - [ 3a + 5b + 7c ] = 70 - 30


=> 4a + 6b + 8c - 3a - 5b - 7c = 40



=> a + b + c = 40
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