Answer :
the name of the missing number is x
then, this number plus 12.8 is equal to 140.8
[tex]x+12.8=140.8[/tex]we can find the missing number if we make a subtract of 12.8 on both sides
[tex]\begin{gathered} x+(12.8-12.8)=140.8-12.8 \\ x+(0)=140.8-12.8 \\ x=128 \end{gathered}[/tex]Value of the unknow is 128