Fill a 10x8 matrix with 80 distinct integers between 1 and 160 (both numbers inclusive) so each of its ten rows adds up to 640, and each of its eight columns adds up to 800.
One solution, out of hundreds of thousands possible:
40 119 118 43 44 115 114 47
120 41 42 117 116 45 46 113
48 111 110 51 52 107 106 55
112 49 50 109 108 53 54 105
56 103 102 59 60 99 98 63
104 57 58 101 100 61 62 97
64 95 94 67 68 91 90 71
96 65 66 93 92 69 70 89
72 87 86 75 76 83 82 79
88 73 74 85 84 77 78 81