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47. 116-(-79)=195
48. 25×100/20=125
49. 14
50. r= 176/2π=28
51. 12x²+4xy-4y²
52 9×25=225
Step-by-step explanation:
1.166-79
2. 20÷100×25
3.2-1÷7
4.176÷2