Answer:
Step-by-step explanation:
Conditions
Let the girls = g
Let the boys = b
Equations
g + b = 1280
g = b + 70
Solution
Put the value for the girls (second equation) into the first equation.
b + 70 + b = 1280 Subtract 70 from both sides
b + 70 - 70 + b = 1280 -70 Combine
2b = 1210 Divide both sides by 2
2b/2 = 1210/2
b = 605 Substitute this value into the top equation
g + 605 = 1280 Subtract 605 from both sides
g + 605 - 605 = 1280 - 605
g = 675
Answer
# boys = 605
# girls = 675
