<human>:  Barry wants to make a huge salad using only cucumbers and tomatoes. He will use a total of 280 pieces of vegetables. If there are thrice as many tomatoes as cucumbers, how many cucumbers will be used in the salad?
<bot>: Define a variable ** Let c be the number of cucumbers and t the number of tomatoes.
Write an equation ** The total is the sum of the number of cucumbers and that of tomatoes, which is c + t = 280 piece of vegetables
How many cucumbers are there? ** Since there are thrice as many tomatoes as cucumbers, this means c =t/3
How many cucumbers are there? ** Therefore 3*c = t.
Write an equation ** The sum will therefore be c + 3*c = 280 pieces of vegetables
Simplify ** This means that 4*c = 280 vegetables
How many cucumbers are there? ** Therefore c = 280/4 = <<280/4=70>>70 cucumbers.
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