Question

1/5 of a number is decreased by 5 is 16 find the number

Answer 1

let the number be x.
so 1/5 of the number= x/5
5 decreased from x/5= x/5-5
result=16
so 
x/5-5=16
x/5=16+5
x/5=21
now by cross multiplication
x=21*5
Hence x= 105

Answer 2

let x be the number
given 1/5x-5=16
x/5=21
x=105