<span>-7+..3.= -4 </span>
<span><span>-7+(-3)= -10</span></span>
<span><span><span>7+(-3)=4</span></span></span>
<span><span><span><span>(-9)+8=-1</span></span></span></span>
<span><span><span><span><span>(-9)+(-8) = -17</span></span></span></span></span>
<span><span><span><span><span><span>9+(-8)=1</span></span></span></span></span></span>
<span><span><span><span><span><span><span>9+(-9)=0</span></span></span></span></span></span></span>
<span><span><span><span><span><span><span><span>(-11)+11=0</span></span></span></span></span></span></span></span>
<span><span><span><span><span><span><span><span><span>-12+12=0 </span></span></span></span></span></span></span></span></span>