Answer:
8700kg
Explanation:
b = mass of bricks
l = mass of lorry
b+l = total mass = 11600kg
b = 3l ==> l = b/3
substitute: b + b/3 = 11600
multiply every term by 3 to get rid of denominator: 3b + b = 34800
simplify and solve: 4b = 34800 ==> b = 8700
check: l = 8700/3 = 2900
2900 + 8700 = 11600? YES