Solution 1.1:1b

We start by working out the expressions inside the brackets,

\displaystyle 3-\bbox[#FFEEAA;,1.5pt]{\,(7-4)\,}+\bbox[#FFEEAA;,1.5pt]{\,(6-5)\,} = 3-\bbox[#FFEEAA;,1.5pt]{\,3\,}+\bbox[#FFEEAA;,1.5pt]{\,1\,}.

Then, all we have to do is to combine the numbers

\displaystyle \phantom{3-\bbox[#FFEEAA;,1.5pt]{\,(7-4)\,}+\bbox[#FFEEAA;,1.5pt]{\,(6-5)\,}}{} = \firstcbox{#FFEEAA;}{\,3-3\,}{0}+1

\displaystyle \phantom{3-\bbox[#FFEEAA;,1.5pt]{\,(7-4)\,}+\bbox[#FFEEAA;,1.5pt]{\,(6-5)\,}}{} = \secondcbox{#FFEEAA;}{\,3-3\,}{0}+1

\displaystyle \phantom{3-\bbox[#FFEEAA;,1.5pt]{\,(7-4)\,}+\bbox[#FFEEAA;,1.5pt]{\,(6-5)\,}}{} = 1\,\mbox{.}