16)
83 + 86 + 91 + 77 + x = 5(85)
x+ 337 = 425
x = 425 -337
x = 88
answer: last test he needs to make 88
17)
x+y = 5000; x = 5000 - y
0.045x + 0.06y = 270
substitute x = 5000 - y into 0.045x + 0.06y = 270
0.045x + 0.06y = 270
0.045(5000 - y) + 0.06y = 270
225 - 0.045y + 0.06y = 270
0.015y = 45
y = 3000
x = 5000 - 3000 = 2000
answer:
he invested $2,000 in checking account and $3,000 in savings account
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double check
0.045x + 0.06y = 270
0.045(2000) + 0.06(3000) = 270
90 + 180 = 270
270 = 270