One piece will be length x and the other piece will be 20 cm longer, so it will be x + 20 cm long. . Added together the length of these two boards will equal 86 cm. So you can write an equation: . x + (x + 20) = 86 . Remove the parentheses and add the two x's together to get: . 2x + 20 = 86

Subtract 20 from both sides: . 2x = 66 . Divide both sides by 2 and you have: . x = 33 . The short piece is 33 cm and the other piece is 20 cm longer or 33 + 20 = 53 cm. . As a check you can add 33 + 53 to make sure that the lengths of these two pieces add up to be the total length of the original board, 86 cm.