The is 73 %.
The formula for percent yield is
$color(blue)(bar(ul(|color(white)(a/a) "Percent yield" = "actual yield"/"theoretical yield" × 100 %color(white)(a/a)|)))" "$
∴ $"Percent yield" = (19 color(red)(cancel(color(black)("g"))))/(26 color(red)(cancel(color(black)("g")))) × 100 % = 73 %$