First find the total number of tomatoes harvested: 18 plants * 7 tomatoes/plant = <<18*7=126>>126 tomatoes
Then divide that number by 2 to find how many tomatoes are left undried: 126 tomatoes / 2 = <<126/2=63>>63 tomatoes
Then divide that number by 3 to find how many tomatoes are turned into sauce: 63 tomatoes / 3 = <<63/3=21>>21 tomatoes
Then subtract that number from the number of undried tomatoes to find the remaining number of tomatoes: 63 tomatoes - 21 tomatoes = <<63-21=42>>42 tomatoes
#### 42