“PROOF WITHOUT WORDS: $\frac{a}{b}=\frac{c}{d} \Rightarrow \frac{a}{b}=\frac{c}{d}=\frac{a \pm c}{b \pm d}$ IN THE RANGE OF NATURAL NUMBERS”. 2022. Far East Journal of Mathematical Education 22 (June): 29-32. https://doi.org/10.17654/0973563122006.