First of all, let's plug the values. You simply have to substitute every occurrence of "x" with "7" and every occurrence of "y" with "-3", which leads to
[tex] -4|x+5y| \to -4|7+5\cdot (-3)| = -4|7-15| = -4|-8| [/tex]
Now, the absolute value of a number [tex] x [/tex], i.e. [tex] |x| [/tex], returns the positive versione of a number. So, if x is positive, you have [tex] |x| = x [/tex] whereas if x is negative you have [tex] |x| = -x [/tex].
In this case, the absolute value of -8 is 8, because -8 is negative. So, the expression becomes
[tex]-4|-8| = -4 \cdot 8 = -32[/tex]
