how to find difference between two figures like 5-2= difference is 3 using formula

[himaninayak]

Hi, 

my name is Himani and I am working on an excel sheet and I am trying a formula for find out the difference between two weeks data , but it isn't working, If anyone knows how to do that please help me with that. I am attaching the screenshot for reference. 

Thank you in advance. 

[#2]

@himaninayak 

The values in columns D and E are text values.

Perhaps the following in F12:

=SUBSTITUTE(D12, " m3", "")-SUBSTITUTE(D7, " m3", "")

Fill down.

[#3]

Thank you, let me try that.