<human>:  Krissa needs to order field trip shirts for her preschool students. 11 students need size extra-small. Twice as many students need size small as extra small. Four less than the number of size small students need size medium. Half as many students need size large as size medium. Six more students need size extra-large than large. Altogether, how many shirts did Krissa order?
<bot>: How many size small shirts did Krissa order? ** Krissa ordered 11 x 2 = <<11*2=22>>22 size small.
How many size medium shirts did Krissa order? ** She ordered 22 - 4 = <<22-4=18>>18 size medium.
How many size large shirts did Krissa order? ** She ordered 18 / 2 = <<18/2=9>>9 size large.
How many size extra-large shirts did Krissa order? ** She ordered 9 + 6 = <<9+6=15>>15 size extra-large.
How many shirts did Krissa order? ** Altogether, Krissa ordered 11 + 22 + 18 + 9 + 15 = <<11+22+18+9+15=75>>75 shirts.
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