\(If \Diamond4_7=\Diamond1_{8} and \Diamond represents a digit, solve for \Diamond.\)
d47 = 7·d + 4 (changing the number into base ten)
d18 = 8·d + 1 (changing the number into base ten)
Since these are equal: 7d + 4 = 8d + 1
3 = d
347 = 7·3 + 4 = 25
318 = 8·3 + 1 = 25
