$a)$

$6^2=6\cdot 6=36$

$3^3=3\cdot 3\cdot 3=9\cdot 3=27$

$8^2=8\cdot 8=64$

$7^2=7\cdot 7=49$

 

$b)$

${10}^2=10\cdot 10=100$

${100}^3=100\cdot 100\cdot 100=1000000$

${1000}^2=1000\cdot 1000=1000000$

 

$c)$

${30}^2=30\cdot 30=900$

${60}^2=60\cdot 60=3600$

${50}^3=50\cdot 50\cdot 50=2500\cdot 50=125000$

${90}^2=90\cdot 90=8100$