[tex]\frac{12}{90}=\frac{12:2}{90:2}=\frac{6}{45}=\frac{6:3}{45:3}=\frac{2}{15}\\\\\frac{84}{126}=\frac{84:2}{126:2}=\frac{42}{63}=\frac{42:21}{63:21}=\frac{2}{3}\\\\\frac{165}{225}=\frac{165:5}{225:5}=\frac{33}{45}=\frac{33:3}{45:3}=\frac{11}{15}[/tex]