Across
1
Mathematical rule or equation
4
Rectangle with four equal sides
5
Number less than zero
6
Three-sided polygon
12
Difference between highest and lowest values
Down
2
Reference line in a graph
3
Number with digits after a point
7
Single numeral from 0 to 9
8
Symbol representing unknown value
9
Exact correspondence on both sides
10
Line crossing from corner to corner
11
Lines that never intersect