18•4=AD•PB

Are you using AD and PB as:

1. two-digit numbers (AD = 10A + D and PB = 10P + B), or
2. products of digits (AD = A × D and PB = P × B)?

If (1) two-digit numbers: there is no solution, because 18 × 4 = 72 and the right side would be (two-digit) × (two-digit) ≥ 10 × 10 = 100.

If (2) products of digits (AD = A × D and PB = P × B): you need (A × D) × (P × B) = 72. One simple distinct-digit example is:

• A = 1, D = 4, P = 3, B = 6
• Then AD = 1×4 = 4 and PB = 3×6 = 18, so AD × PB = 4 × 18 = 72, which matches 18 × 4.

Other distinct-digit solutions (by permuting A, D, P, B) include:

• A=1, D=3, P=4, B=6 (AD=3, PB=24)
• A=3, D=4, P=1, B=6 (AD=12, PB=6)
• A=3, D=6, P=4, B=1 (AD=18, PB=4)
• A=4, D=6, P=1, B=3 (AD=24, PB=3)

If you tell me which interpretation you’re using (and whether digits must be distinct), I can tailor the solution or provide more examples.