To find the value of "plus" in the equation "plus -15.6 equals 22.3", you can set up the equation as follows:
\( x - 15.6 = 22.3 \)
Now, to isolate \( x \), you can add 15.6 to both sides of the equation:
\[ x = 22.3 + 15.6 \]
\[ x = 37.9 \]
So, \( 37.9 - 15.6 = 22.3 \). Therefore, the solution is \( 37.9 \).