1
3
addition
algebra
background
black
blackboard
board
business
calculation
chalk
chalkboard
classroom
collaborate
concept
conceptual
cooperate
drawing
education
elementary
equals
error
formula
hand
incorrect
learn
lesson
math
mathematical
mathematics
mistake
number
one
plus
school
sign
study
sum
symbol
synergy
teach
teaching
text
three
together
white
work
write
writing
wrong