What does this : mean

Step-by-step explanation:

That character ( : ) is the 'colon" and in math it represents "ratio."

For example, "the ratio of 5 to 7" would be written 5:7

A colon in math interpretation is usually used in ratios and ratio charts.

The colon is used in mathematics, cartography, model building, and other fields—in this context it denotes a ratio or a scale, as in 3:1.

a reflection across the x-axis , followed by the by a reflection across the y-axis , and then a scale dilation of 0.5 .