7 W + 4 X = 36
8 W + 5 X = 42
Fill in the blanks.
- 1 W = _____
- 1 X = _____
- 2 W + 4 X = _____
(a)
7 W + 4 X = 36 --- (1)
8 W + 5 X = 42 --- (2)
Make X the same.
LCM of 4 and 5 = 20
(1) x 5
35 W + 20 X = 180 --- (3)
(2) x 4
32 W + 20 X = 168 --- (4)
(a)
(3) - (4)
(35 W + 20 X) - (32 W + 20 X) = 180 - 168
35 W - 32 W + 20 X - 20 X = 12
3 W = 12
1 W = 12 ÷ 3 = 4
(b)
Substitute W = 4 into (1).
7 W + 4 X = 36
7 x 4 + 4 X = 36
28 + 4 X = 36
4 X = 36 - 28 = 8
1 X = 8 ÷ 4 = 2
(c)
2 W + 4 X
= 2 x 4 + 4 x 2
= 8 + 8
= 16
Answer(s): (a) 4; (b) 2; (c) 16