Naomi S. answered • 09/04/18

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Number of teachers = n

Total salary = x

Average = x / n

3000 = x / n

x = 3000 n --------eq 1

when salary of 2 more teachers is included, the average salary reduce by rs 100 and the total salary increased by rs 4000

3000 -100 =( x + 4000) / (n + 2)

2900 = (x+4000)/(n+2)

2900(n+2) = (x+4000)

2900n +5800 = 3000n +4000 -----------from eq 1

100n =1800

n =18

so number of teachers =n= 18