3. Viết vào ô trống (theo mẫu):

a

5

10

20

$25+a$

$25+5=30$

c

2

5

10

$296–c$

$296–2=294$

a

5

10

20

$25+a$

$25+5=30$

$25+10=35$

$25+20=45$

c

2

5

10

$296–c$

$296–2=294$

$296–5=291$

$296–10=286$