This will give you mark1=90 as result:
VB.Net Code:
'regex with 1 capture group: (.*)
Dim srgx As New System.Text.RegularExpressions.Regex("(.*)\sFor English3 & English2")
'text you need to parse
Dim tmpstring As String = "mark1=90 For English3 & English2"
'Find Capture Group in:
Dim matchG As System.Text.RegularExpressions.MatchCollection = srgx.Matches(tmpstring)
MsgBox(matchG(0).Groups(1).ToString())
If you had multiple different entry strings, let me know to make a little change to above code, but then I will need a few more samples...