(23) 7×10¹ + 3×1 = 70 + 3 = 73
(25) 3×10² + 8×10¹ + 5×1 = 300 + 80 + 5 = 385
(27) 5×10⁵ + 2×10⁴ + 8×10³ + 7×10² + 4×10¹ + 3×1 = 500000 + 20000 + 8000 + 700 + 40 + 3 = 528743
It should be quite clear what you have to do from here, I think.
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