[basic.fundamental] Format "N" consistently (#8637)

Author: lprv

source/basic.tex

@@ -5398,7 +5398,7 @@
 there exists a corresponding \defnadj{extended unsigned integer}{type}.
 The standard and extended unsigned integer types
 are collectively called \defnadjx{unsigned integer}{types}{type}.
-An unsigned integer type has the same width \placeholder{N}
+An unsigned integer type has the same width $N$
 as the corresponding signed integer type.
 \indextext{arithmetic!\idxcode{unsigned}}%
 The range of representable values for the unsigned type is
@@ -5444,7 +5444,7 @@
 The width of each standard signed integer type
 shall not be less than the values specified in \tref{basic.fundamental.width}.
 The value representation of a signed or unsigned integer type
-comprises $N$ bits, where N is the respective width.
+comprises $N$ bits, where $N$ is the respective width.
 Each set of values for any padding bits\iref{basic.types.general}
 in the object representation are
 alternative representations of the value specified by the value representation.