To decrease 5 1/4 m (5.25 m) by 50 cm, you first convert 50 cm to m.
To convert cm to m, you divide cm by 100:
[tex]\frac{cm}{100}=m[/tex]
So you can do:
[tex]\frac{50cm}{100}=0.5m[/tex]
Now that you know 50 cm is 0.5 m, you can subtract 5.25 m by 0.5 m:
5.25 m - 0.5 m = 4.75 m or [tex]4\frac{3}{4}[/tex] m