The formula for the heat absorbed by a substance is
$color(blue)(|bar(ul(color(white)(a/a) q = mcΔT color(white)(a/a)|)))" "$
where
$q$ is the quantity of heat
$m$ is the mass of the substance
$c$ is the specific heat capacity of the material
$ΔT$ is the temperature change
You can rearrange the formula to calculate the specific heat capacity:
$c = q/(mΔT)$
$ΔT = "(20 - 0) °C" = "20 °C"$
$c = "35.2 J"/"4.0 g × 20 °C" = "0.44 J·°C"^"-1""g"^"-1"$