You're looking for an inequality of the form [tex]|t-b|\le a[/tex], or [tex]-a\le t-b\le a[/tex], or [tex]b-a\le t\le b+a[/tex].
Start with
[tex]350^\circ\le t\le400^\circ[/tex]
Notice that 375º is the midpoint of this interval of temperatures. If we subtract all sides by 375º, then we get
[tex]-25^\circ\le t-375^\circ\le25^\circ[/tex]
so we can set [tex]a=25^\circ[/tex] and [tex]b=375^\circ[/tex], and we can rewrite this inequality in terms of absolute values as
[tex]|t-375^\circ|\le25^\circ[/tex]
