Question

afla numarul necunoscut :1020 + ( d - 2021 ) = 4878

Answer 1

1020+(d-2021)=4878
d-2021=4878-1020
d-2021=3858
d=3858+2021
d=5879

Answer 2

$1~020+(d-2~021)=4~878 \\ d-2~021=4~878-1~020 \\ d-2~021=3~858 \\ d=3~858+2~021\\ \boxed{\bold{d=5~879}}$