Answer:
Rob is 76 cm tall.
Step-by-step explanation:
Let b = height of bill.
Let m = height of Mary.
Let r = height of Rob.
"the total heigh of bill mary and rob is 180 cm"
b + m + r = 180 Equation 1
"bob* is twice as tall as bill"
*I think you meant Rob is twice as tall as Bill.
r = 2b
"mary is 28 cm taller than bill"
m = b + 28
Substitue r = 2b and m = b + 28 into Equation 1.
b + b + 28 + 2b = 180
4b + 28 = 180
4b = 152
b = 38
r = 2b
r = 2(38) = 76
Rob is 76 cm tall.
Answer:
76 cm
Step-by-step explanation:
The total height is 180 cm. We set Bill as x. Rob is 2x. Mary is 28+x.
x + 2x + (28+x) = 180
4x +28 = 180
4x = 152
x = 38
This means that Bill is 38 cm. Rob is 2x.
2x = 2(38) = 76
