a)

Wiemy, że:

$\underset{1\text{dm}\cdot 1\text{dm}}{\underbrace{1{\text{dm}}^2}}=\underset{10\text{cm}\cdot 10\text{cm}}{\underbrace{100{\text{cm}}^2}}$

Zatem:

$28{\text{dm}}^2=28\cdot 100{\text{cm}}^2=\boxed{2800}{\text{cm}}^2$

---

b)

Wiemy, że:

$\underset{1\text{m}\cdot 1\text{m}}{\underbrace{1{\text{m}}^2}}=\underset{100\text{cm}\cdot 100\text{cm}}{\underbrace{10000{\text{cm}}^2}}$

Zatem:

$2,4{\text{m}}^2=2,4\cdot 10000{\text{cm}}^2=\boxed{24000}{\text{cm}}^2$

---

c)

Wiemy, że:

$\underset{1\text{cm}\cdot 1\text{cm}}{\underbrace{1{\text{cm}}^2}}=\underset{10\text{mm}\cdot 10\text{mm}}{\underbrace{100{\text{mm}}^2}}$

Zatem:

$3,8{\text{cm}}^2=3,8\cdot 100{\text{mm}}^2=\boxed{380}{\text{mm}}^2$

---

d)

Wiemy, że:

$\underset{1\text{dm}\cdot 1\text{dm}}{\underbrace{1{\text{dm}}^2}}=\underset{10\text{cm}\cdot 10\text{cm}}{\underbrace{100{\text{cm}}^2}}$

Zatem:

$52,7{\text{dm}}^2=52,7\cdot 100{\text{cm}}^2=\boxed{5270}{\text{cm}}^2$

---

e)

Wiemy, że:

$\underset{1\text{km}\cdot 1\text{km}}{\underbrace{1{\text{km}}^2}}=\underset{1000\text{m}\cdot 1000\text{m}}{\underbrace{1000000{\text{m}}^2}}$

Zatem:

$0,029{\text{km}}^2=0,029\cdot 1000000{\text{m}}^2=\boxed{29000}{\text{m}}^2$

---

f)

Wiemy, że:

$\underset{1\text{dm}\cdot 1\text{dm}}{\underbrace{1{\text{dm}}^2}}=\underset{10\text{cm}\cdot 10\text{cm}}{\underbrace{100{\text{cm}}^2}}$

Zatem:

$6200{\text{cm}}^2=\frac{6200}{100}{\text{dm}}^2=\boxed{62}{\text{dm}}^2$

---

g)

Wiemy, że:

$\underset{1\text{cm}\cdot 1\text{cm}}{\underbrace{1{\text{cm}}^2}}=\underset{10\text{mm}\cdot 10\text{mm}}{\underbrace{100{\text{mm}}^2}}$

Zatem:

$750{\text{mm}}^2=\frac{750}{100}{\text{cm}}^2=\boxed{7,5}{\text{cm}}^2$

---

h)

Wiemy, że:

$\underset{1\text{m}\cdot 1\text{m}}{\underbrace{1{\text{m}}^2}}=\underset{100\text{cm}\cdot 100\text{cm}}{\underbrace{10000{\text{cm}}^2}}$

Zatem:

$6375{\text{cm}}^2=\frac{6375}{10000}{\text{m}}^2=\boxed{0,6375}{\text{m}}^2$

---

i)

Wiemy, że:

$\underset{1\text{km}\cdot 1\text{km}}{\underbrace{1{\text{km}}^2}}=\underset{1000\text{m}\cdot 1000\text{m}}{\underbrace{1000000{\text{m}}^2}}$

Zatem:

$59000{\text{m}}^2=\frac{59000}{1000000}{\text{km}}^2=\boxed{0,059}{\text{km}}^2$