MySQL 8.0

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.

select version();

-- create database if not exists demo;

-- use demo;
create table Todo_tbl (
id INT auto_increment,
person VARCHAR(45) ,
task VARCHAR(45) ,
duration INT(4),
deadline_day VARCHAR(2),
deadline_month VARCHAR(2),

PRIMARY KEY(id)
)ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=latin1;

insert into Todo_tbl values(1,'John', 'dust the floors', 40,04,03);
insert into Todo_tbl values(2,'Matt', 'do the dishes', 15,02,02);
insert into Todo_tbl values(3,'Mary', 'dusting', 40,03,02);
insert into Todo_tbl values(4,'Chloe', 'cleaning the windows', 65,04,05);
insert into Todo_tbl values(5,'John', 'wash the floors', 60,03,03);
insert into Todo_tbl values(6,'Bridget', 'take out the trash', 15,03,03);
insert into Todo_tbl values(7,'Matt', 'do the laundry', 18,02,02);
insert into Todo_tbl values(8,'Bridget', 'water the plants', 15,03,03);

select * from Todo_tbl;

/*
create table Statistics_tbl with (
SELECT Todo_tbl.person, SUM(Todo_tbl.duration) FROM Todo_tbl JOIN Statistics_tbl 
on Todo_tbl.person = Statistics_tbl.person GROUP BY person;
);
*/

create table Statistics_tbl (person VARCHAR(45), sum_duration INT)
    SELECT Todo_tbl.person, SUM(Todo_tbl.duration) sum_duration
    FROM Todo_tbl
    GROUP BY person;

select * from Statistics_tbl;

version()
8.0.30

id	person	task	duration	deadline_day	deadline_month
1	John	dust the floors	40	4	3
2	Matt	do the dishes	15	2	2
3	Mary	dusting	40	3	2
4	Chloe	cleaning the windows	65	4	5
5	John	wash the floors	60	3	3
6	Bridget	take out the trash	15	3	3
7	Matt	do the laundry	18	2	2
8	Bridget	water the plants	15	3	3

Records: 5  Duplicates: 0  Warnings: 0

person	sum_duration
John	100
Matt	33
Mary	40
Chloe	65
Bridget	30