what is the answer to 10x+y=-85? this also has to apply to 0.1x+2.5y=11.6

Question

I do not understand the elimination or substitution methods and cannot solve this problem.

Answer 1

Multiply the 2nd equation through by 10 to get rid of the decimal points: x+25y=116. So x=116-25y. Substitute this value of x in the first equation: 1160-250y+y=-85. Add 85 to each side and combine the y terms: 1245-249y=0, so 249y=1245 and y=1245/249=5. To find x, substitute the y value: x=116-125=-9. Check these out in the equation with the decimals: 0.1*(-9)+2.5*5=12.5-0.9=11.6. And in the other equation: -90+5=-85. Both check out!