7 Martina has three lorry loads of paving slabs. There are x paving slabs on lorry A. There are (2x-1) paving slabs on lorry B. There are (3x+5) paving slabs on lorry C. There is a total of 58 paving slabs on the three lorries. All the paving slabs have the same mass. The paving slabs on lorry B have a total mass of 680 kg. Work out the total mass of the paving slabs on lorry A.

Beginning with the number of slabs, we need to solve the equation to find the value of , since the total number of slabs on all three lorries is 58.After finding the number of slabs on lorry B, which is , we can determine that the mass of one slab is kilograms, since we know the total mass of the slabs on lorry B.Finally, with the mass of a single slab determined, we can find the total mass of the slabs on lorry A, which would be \(x × \ (\frac{680}{2x-1})\).