Let R = number of Rows

Let T = number of Trees per row

Since number of trees in each row is 4 less than twice the number of rows we have:

T = 2R - 4

We are told that the total trees is 198:

Total trees = R * T

R*T = 198

Plug T = 2R - 4 into R*T = 198:

R*(2R - 4) = 198

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click here to see the quadratic equation solved for R

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R = 11 rows

We need to ignore the negative solution -9 since the number of rows is always positive number.

T = 2*11 - 4

T = 18 trees

There are 11 rows and 18 trees per row.