To solve this problem we just have to add the opposite number to the number inside the parenthesis (next to the blank space) on both sides of the equation, the x will represent the blank space
a)
[tex]\begin{gathered} x+(-25)=34 \\ x+(-25)+25=34+25 \\ x+0=59 \\ x=59 \end{gathered}[/tex]
The unknown number is 59.
b)
[tex]\begin{gathered} x+26=12 \\ x+26-26=12-26 \\ x=-14 \end{gathered}[/tex]
The unknown number is -14.
c)
[tex]\begin{gathered} 8+x=-24 \\ 8-8+x=-24-8 \\ x=-32 \end{gathered}[/tex]
The unknown number is -32.
d)
[tex]\begin{gathered} -12+x=-24 \\ -12+12+x=-24+12 \\ x=-12 \end{gathered}[/tex]
The unknown number is -12.
e)
[tex]\begin{gathered} -15+x=-28 \\ -15+15+x=-28+15 \\ x=-13 \end{gathered}[/tex]
The unknown number is -13.
f)
[tex]\begin{gathered} x+18=-3 \\ x+18-18=-3-18 \\ x=-21 \end{gathered}[/tex]
The unknown number is -21.
