Robert needs to cut four shelves from a board that is 2.5 meters long. the second shelf is 18 cm longer than twice the length of the first shelf. the remaining shelf is 4 centimeters longer than the first shelf. if robert must use the entire board for the shelves, what is the length of the second shelf, in cm

STEP 1:
convert meters to centimeters
100 cm= 1 meter

= 100 cm/m * 2.5 m
= 250 cm

STEP 2:
x= length of first shelf
2x+18= length of second shelf
x-12= length of third shelf
x+4= length of fourth shelf

since the whole board has to be used, add lengths of all shelves and set it equal to the whole length of the board (250 cm).

x + (2x+18) + (x-12) + (x+4)= 250 cm
combine like terms
5x + 10= 250
subtract both sides by 10
5x= 240
divide both sides by 5
x= 48

STEP 3:
find length of second shelf
= 2x + 18
= 2(48) + 18
= 114 cm

CHECK:
x + (2x+18) + (x-12) + (x+4)= 250
48 + (2(48)+18) + (48-12) + (48+4)= 250
48 + (96+18) + 36 + 52= 250
48 + 114 + 36 + 52= 250
250= 250

ANSWER: Shelf two is 114 cm.

Hope this helps! :)