How do you convert a fraction with a nuemartor as 1 and denominator of 5into a decimal?

You can either use long division or make the denomenator a power of 10 (10,100,1000,etc)
because, remember

0.1= a tenth=1/10
0.01=a hundreth=1/100

so

1/5=x/10
cross multiply
2=x
x/10=tenths
2/10=2 tenths=0.2

answer is 0.2

That. you would have multiple