$a)3\cdot {10}^{-6}=3\cdot 0,000001=0,000003$

$3\cdot {10}^{-6}>0,0000003$

$b)4,3\cdot {10}^{-7}=4,3\cdot 0,0000001=0,00000043$

$4,3\cdot {10}^{-7}<0,00000048$  

$c)5,2\cdot {10}^{-8}=5,2\cdot 0,00000001=0,000000052$  

$5,2\cdot {10}^{-8}=0,000000052$  

$d)4,1\cdot {10}^{-7}=4,1\cdot 0,0000001=0,00000041$  

$4,1\cdot {10}^{-7}<0,0000041$