Table:
0
A
B
C
D
E
1
Region/country
1985-1990
1990-1995
1995-2000
2000-2005
2
Asia
3.78
3.09
2.88
2.61
3
South-East Asia
4.11
3.99
3.84
3.40
4
East Asia
4.08
3.08
2.82
2.52
5
China
5.04
3.77
3.52
3.08
6
Europe
0.78
0.37
0.14
0.13
7
North America
1.24
0.57
1.51
1.37
8
Oceania
1.52
1.52
1.46
1.40

Questions and formulas:
Question: what's the 1985-1990 with 1995-2000 being 1.46
Formula: SUM(FILTER(B1, D1=1.46))
Formula2: SUM(FILTER(B2:B8, D2:D8=1.46))
Level: easy
Question: what's the 2000-2005 with 1985-1990 being 3.78
Formula: SUM(FILTER(E1, B1=3.78))
Formula2: SUM(FILTER(E2:E8, B2:B8=3.78))
Level: easy
Question: what's the 1985-1990 with 2000-2005 being 2.52
Formula: SUM(FILTER(B1, E1=2.52))
Formula2: SUM(FILTER(B2:B8, E2:E8=2.52))
Level: easy
Question: what's the region/country with 2000-2005 being 2.61
Formula: LET(query1,SUMMARIZE(A1,SUMX(E1)),FILTER(query1,CHOOSECOLS(query1,2)=2.61))
Formula2: LET(query1,SUMMARIZE(A2:A8,SUMX(E2:E8)),FILTER(query1,CHOOSECOLS(query1,2)=2.61))
Level: hard
Question: what's the 1995-2000 with 1985-1990 being 1.24
Formula: SUM(FILTER(D1, B1=1.24))
Formula2: SUM(FILTER(D2:D8, B2:B8=1.24))
Level: easy
Question: what's the 1995-2000 with 1990-1995 being 3.08
Formula: SUM(FILTER(D1, C1=3.08))
Formula2: SUM(FILTER(D2:D8, C2:C8=3.08))
Level: easy