To find the number that, when added to 5.22, equals 1.57, you can set up the equation:
\( x + 5.22 = 1.57 \)
To solve for \( x \), subtract 5.22 from both sides:
\( x = 1.57 - 5.22 \)
Calculating this gives:
\( x = -3.65 \)
So, \(-3.65\) plus \(5.22\) equals \(1.57\).