Question 1013421
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150A+115B=10 tonnes . Multiply this by 2.
300A+230B=20 tonnes
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300A+30B=10 tonnes , Subtract this from above
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200B=10 tonnes
B=10tonnes/200
B=1/20 tonne
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150A+115B=10 tonnes
150A+115(1/20 tonne)=10 tonnes
150A+115/20 tonnes=10 tonnes
150A=200/20 tonnes-115/20 tonnes
150A=85/20 tonnes
A=85/3000 tonnes
A=17/600 tonnes
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ANSWER: Box A weighs 17/600 tonne; Box B weighs 1/20 tonne 
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CHECK:
300A+30B=10 tonnes
300(17/600)+30(1/20)=10 tonnes
(17/2)+(3/2)=10 tonnes
20/2 tonnes=10 tonnes
10 tonnes=10 tonnes
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